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Sometime in late 2007, we had the idea of a DTrace conference. Or really, more of a meetup; from the primordial e-mail I sent: The goal here, by the way, is not a DTrace user group, but more of a face-to-face meeting with people actively involved in DTrace — either by porting it to another system, by integrating probes into higher level environments, by building higher-level tools on top of DTrace or by using it heavily and/or in a critical role. That said, we also don’t want to be exclusionary, so our thinking is that the only true requirement for attending is that everyone must be prepared to speak informally for 15 mins or so on what they are doing with DTrace, any limitations that they have encountered, and some ideas for the future. We’re thinking that this is going to be on the order of 15-30 people (though more would be a good problem to have — we’ll track it if necessary), that it will be one full day (breakfast in the morning through drinks into the evening), and that we’re going to host it here at our offices in San Francisco sometime in March 2008. This same note also included some suggested names for the gathering, including what in hindsight seems a clear winner: DTrace Bi-Mon-Sci-Fi-Con. As if knowing that I should leave an explanatory note to my future self as to why this name was not selected, my past self fortunately clarified: "before everyone clamors for the obvious Bi-Mon-Sci-Fi-Con, you should know that most Millennials don’t (sadly) get the reference." (While I disagree with the judgement of my past self, it at least indicates that at some point I cared if anyone got the reference.) We settled on a much more obscure reference, and had the first dtrace.conf in March 2008. Befitting the style of the time, it was an unconference (a term that may well have hit its apogee in 2008) that you signed up to attend by editing a wiki. More surprising given the year (and thanks entirely to attendee Ben Rockwood), it was recorded — though this is so...
5th Dec 2024

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More from Oxide Computer Company Blog

Systems Software in the Large

Software is hard (yes, even in an era of vibe coding), and systems software — the silent engine room of modern infrastructure — is especially so. By design, systems software provides an abstraction for programs, insulating programmers from the filthy details that lie beneath; piercing that abstraction to implement the underlying system is to embrace those details and their gnarly implications. Moreover, the expectation for systems software is (rightly) perfection; a system that is merely functional can be deceptively distant from the robustness required of foundational software. Systems software isn’t the only kind of hard software, of course, and indeed software can be difficult just by nature of its scope and composition: it is hard to build software that is just…​ big. Software that consists of many different modules and components built by multiple people over an extended period of time is known as programming in the large, and its difficulties extend beyond the mere implementation challenges of systems software. Because the difficulties with developing systems software are broadly orthogonal to those of programming in the large, intersecting these two challenges — that is, developing systems software in the large — is to take on the most grueling of projects: it is the stuff of which mythical man months are literally made. Why would anyone ever develop such a system? Because they are often necessary to tackle software’s equivalents of the wicked problem: problems that are not only never completely solved, but also not even really understood until implementation is well underway. There are not pat answers for developing these systems — nor, infamously, silver bullets — they’re just…​ brutal. This is on my mind because of a talk that we had at OxCon last week. OxCon is our affectionate name for the annual Oxide meetup here in Emeryville, and it’s a highlight of the year for everyone at Oxide. This year more than lived up to our high expectations, replete with cameos from the extraordinary IBM 26 Interpreting Card Punch and the Oakland Ballers. At OxCon we like to both reflect back and look forward, so in that spirit, we asked Oxide engineer Dave Pacheco if he might be willing to present on the project he’s been leading the charge on for the past two years: software update. When we shipped the first Oxide rack two years ago, it had the minimum functionality necessary to update all its software in the field. Our priority was to make this update mechanism robust over all else, and we succeeded in the sense that it is indeed robust — but the experience is not yet the seamless, self-service facility that we have envisioned. Software update for the Oxide rack is exactly the kind of wicked problem that necessitates systems software in the large: it is not merely dynamically overhauling a distributed system, but doing so while remaining operable in the liminal state between the old software and the new. Compounding this was the urgency we felt: delivering self-service update is essential to realize our vision of the cloud experience on premises, and our customers needed it as soon as we could deliver it. As if this weren’t enough, the Oxide update problem has an acute constraint not faced by the public clouds: we need to be able to deliver updates across an air gap — we cannot rely on the public cloud’s hidden crutch of operators and runbooks. It is a problem so wicked, you can practically hear it cackle. Despite the thorniness of the problem, Dave and team had managed to achieve the ambitious milestones that they had set for themselves at OxCon last year, and I was naturally excited for his presentation this year. That said, I wasn’t ready for what was coming: Dave not only described the tremendous work on software update (delving into both the multi-year history of the project and the significant progress since the last OxCon), but also reflected on leading the software update project itself. The result was an absolutely extraordinary talk, not just on the mechanics of software essential to Oxide, but on the unique challenges of systems software in the large. Dave’s talk dripped with hard-won wisdom, running the gamut from maintaining focus (and the looming specter of what Dave calls "organizational procrastination") to fighting scope creep and the mechanics of specific technical decisions. We felt Dave’s talk to be too good to be kept to ourselves — and thanks to our transparency, nothing in it needs to be secret; we are thrilled to be able to make it generally available: This talk is a must watch for anyone doing systems software in the large, containing within it the kind of lessons that are often only learned the hard way. While we think it’s valuable for everyone, should you be the kind of sicko inexplicably drawn to exactly the kind of nasty problems that Dave describes, consider joining us — there is more systems software in the large to be done at Oxide!

18th Sep 2025 23 votes
Our $100M Series B

We don’t want to bury the lede: we have raised a $100M Series B, led by a new strategic partner in USIT with participation from all existing Oxide investors. To put that number in perspective: over the nearly six year lifetime of the company, we have raised $89M; our $100M Series B more than doubles our total capital raised to date — and positions us to make Oxide the generational company that we have always aspired it to be. If this aspiration seems heady now, it seemed absolutely outlandish when we were first raising venture capital in 2019. Our thesis was that cloud computing was the future of all computing; that running on-premises would remain (or become!) strategically important for many; that the entire stack — hardware and software — needed to be rethought from first principles to serve this market; and that a large, durable, public company could be built by whomever pulled it off. This scope wasn’t immediately clear to all potential investors, some of whom seemed to latch on to one aspect or another without understanding the whole. Their objections were revealing: "We know you can build this," began more than one venture capitalist (at which we bit our tongue; were we not properly explaining what we intended to build?!), "but we don’t think that there is a market." Entrepreneurs must become accustomed to rejection, but this flavor was particularly frustrating because it was exactly backwards: we felt that there was in fact substantial technical risk in the enormity of the task we put before ourselves — but we also knew that if we could build it (a huge if!) there was a huge market, desperate for cloud computing on-premises. Fortunately, in Eclipse Ventures we found investors who saw what we saw: that the most important products come when we co-design hardware and software together, and that the on-premises market was sick of being told that they either don’t exist or that they don’t deserve modernity. These bold investors — like the customers we sought to serve — had been waiting for this company to come along; we raised seed capital, and started building. And build it we did, making good on our initial technical vision: We did our own board designs, allowing for essential system foundation like a true hardware root-of-trust and end-to-end power observability. We did our own microcontroller operating system, and used it to replace the traditional BMC. We did our own platform enablement software, eliminating the traditional UEFI BIOS and its accompanying flotilla of vulnerabilities. We did our own host hypervisor, assuring an integrated and seamless user experience — and eliminating the need for a third-party hypervisor and its concomitant rapacious software licensing. We did our own switch — and our own switch runtime — eliminating entire universes of integration complexity and operational nightmares. We did our own integrated storage service, allowing the rack-scale system to have reliable, available, durable, elastic instance storage without necessitating a dependency on a third party. We did our own control plane, a sophisticated distributed system building on the foundation of our hardware and software components to deliver the API-driven services that modernity demands: elastic compute, virtual networking, and virtual storage. While these technological components are each very important (and each is in service to specific customer problems when deploying infrastructure on-premises), the objective is the product, not its parts. The journey to a product was long, but we ticked off the milestones. We got the boards brought up. We got the switch transiting packets. We got the control plane working. We got the rack manufactured. We passed FCC compliance. And finally, two years ago, we shipped our first system! Shortly thereafter, more milestones of the variety you can only get after shipping: our first update of the software in the field; our first update-delivered performance improvements; our first customer-requested features added as part of an update. Later that year, we hit general commercial availability, and things started accelerating. We had more customers — and our first multi-rack customer. We had customers go on the record about why they had selected Oxide — and customers describing the wins that they had seen deploying Oxide. Customers starting landing faster now: enterprise sales cycles are infamously long, but we were finding that we were going from first conversations to a delivered product surprisingly quickly. The quickening pace always seemed to be due in some way to our transparency: new customers were listeners to our podcast, or they had read our RFDs, or they had perused our documentation, or they had looked at the source code itself. With growing customer enthusiasm, we were increasingly getting questions about what it would look like to buy a large number of Oxide racks. Could we manufacture them? Could we support them? Could we make them easy to operate together? Into this excitement, a new potential investor, USIT, got to know us. They asked terrific questions, and we found a shared disposition towards building lasting value and doing it the right way. We learned more about them, too, and especially USIT’s founder, Thomas Tull. The more we each learned about the other, the more there was to like. And importantly, USIT had the vision for us that we had for ourselves: that there was a big, important market here — and that it was uniquely served by Oxide. We are elated to announce this new, exciting phase of the company. It’s not necessarily in our nature to celebrate fundraising, but this is a big milestone, because it will allow us to address our customers' most pressing questions around scale (manufacturing scale, system scale, operations scale) and roadmap scope. We have always believed in our mission, but this raise gives us a new sense of confidence when we say it: we’re going to kick butt, have fun, not cheat (of course!), love our customers — and change computing forever.

30th Jul 2025 48 votes
Oxide’s Compensation Model: How is it Going?

How it started Four years ago, we were struggling to hire. Our team was small (~23 employees), and we knew that we needed many more people to execute on our audacious vision. While we had had success hiring in our personal networks, those networks now felt tapped; we needed to get further afield. As is our wont, we got together as a team and brainstormed: how could we get a bigger and broader applicant pool? One of our engineers, Sean, shared some personal experience: that Oxide’s principles and values were very personally important to him — but that when he explained them to people unfamiliar with the company, they were (understandably?) dismissed as corporate claptrap. Sean had found, however, that there was one surefire way to cut through the skepticism: to explain our approach to compensation. Maybe, Sean wondered, we should talk about it publicly? "I could certainly write a blog entry explaining it," I offered. At this suggestion, the team practically lunged with enthusiasm: the reaction was so uniformly positive that I have to assume that everyone was sick of explaining this most idiosyncratic aspect of Oxide to friends and family. So what was the big deal about our compensation? Well, as a I wrote in the resulting piece, Compensation as a Reflection of Values, our compensation is not merely transparent, but uniform. The piece — unsurprisingly, given the evergreen hot topic that is compensation — got a ton of attention. While some of that attention was negative (despite the piece trying to frontrun every HN hater!), much of it was positive — and everyone seemed to be at least intrigued. And in terms of its initial purpose, the piece succeeded beyond our wildest imagination: it brought a surge of new folks interested in the company. Best of all, the people new to Oxide were interested for all of the right reasons: not the compensation per se, but for the values that the compensation represents. The deeper they dug, the more they found to like — and many who learned about Oxide for the first time through that blog entry we now count as long-time, cherished colleagues. That blog entry was a long time ago now, and today we have ~75 employees (and a shipping product!); how is our compensation model working out for us? How it’s going Before we get into our deeper findings, two updates that are so important that we have updated the blog entry itself. First, the dollar figure itself continues to increase over time (as of this writing in 2025, $207,264); things definitely haven’t gotten (and aren’t getting!) any cheaper. And second, we did introduce variable compensation for some sales roles. Yes, those roles can make more than the rest of us — but they can also make less, too. And, importantly: if/when those folks are making more than the rest of us, it’s because they’re selling a lot — a result that can be celebrated by everyone! Those critical updates out of the way, how is it working? There have been a lot of surprises along the way, mostly (all?) of the positive variety. A couple of things that we have learned: People take their own performance really seriously. When some outsiders hear about our compensation model, they insist that it can’t possibly work because "everyone will slack off." I have come to find this concern to be more revealing of the person making the objection than of our model, as our experience has been in fact the opposite: in my one-on-one conversations with team members, a frequent subject of conversation is people who are concerned that they aren’t doing enough (or that they aren’t doing the right thing, or that their work is progressing slower than they would like). I find my job is often to help quiet this inner critic while at the same time stoking what I feel is a healthy urge: when one holds one’s colleagues in high regard, there is an especially strong desire to help contribute — to prove oneself worthy of a superlative team. Our model allows people to focus on their own contribution (whatever it might be). People take hiring really seriously. When evaluating a peer (rather than a subordinate), one naturally has high expectations — and because (in the sense of our wages, anyway) everyone at Oxide is a peer, it shouldn’t be surprising that folks have very high expectations for potential future colleagues. And because the Oxide hiring process is writing intensive, it allows for candidates to be thoroughly reviewed by Oxide employees — who are tough graders! It is, bluntly, really hard to get a job at Oxide. It allows us to internalize the importance of different roles. One of the more incredible (and disturbingly frequent) objections I have heard is: "But is that what you’ll pay support folks?" I continue to find this question offensive, but I no longer find it surprising: the specific dismissal of support roles reveals a widespread and corrosive devaluation of those closest to customers. My rejoinder is simple: think of the best support engineers you’ve worked with; what were they worth? Anyone who has shipped complex systems knows these extraordinary people — calm under fire, deeply technical, brilliantly resourceful, profoundly empathetic — are invaluable to the business. So what if you built a team entirely of folks like that? The response has usually been: well, sure, if you’re going to only hire those folks. Yeah, we are — and we have! It allows for fearless versatility. A bit of a corollary to the above, but subtly different: even though we (certainly!) hire and select for certain roles, our uniform compensation means we can in fact think primarily in terms of people unconfined by those roles. That is, we can be very fluid about what we’re working on, without fear of how it will affect a perceived career trajectory. As a concrete example: we had a large customer that wanted to put in place a program for some of the additional work they wanted to see in the product. The complexity of their needs required dedicated program management resources that we couldn’t spare, and in another more static company we would have perhaps looked to hire. But in our case, two folks came together — CJ from operations, and Izzy from support — and did something together that was in some regards new to both of them (and was neither of their putative full-time jobs!) The result was indisputably successful: the customer loved the results, and two terrific people got a chance to work closely together without worrying about who was dotted-lined to whom. It has allowed us to organizationally scale. Many organizations describe themselves as flat, and a reasonable rebuttal to this are the "shadow hierarchies" created by the tyranny of structurelessness. And indeed, if one were to read (say) Valve’s (in)famous handbook, the autonomy seems great — but the stack ranking decidedly less so, especially because the handbook is conspicuously silent on the subject of compensation. (Unsurprisingly, compensation was weaponized at Valve, which descended into toxic cliquishness.) While we believe that autonomy is important to do one’s best work, we also have a clear structure at Oxide in that Steve Tuck (Oxide co-founder and CEO) is in charge. He has to be: he is held accountable to our investors — and he must have the latitude to make decisions. Under Steve, it is true that we don’t have layers of middle management. Might we need some in the future? Perhaps, but what fraction of middle management in a company is dedicated to — at some level — determining who gets what in terms of compensation? What happens when you eliminate that burden completely? It frees us to both lead and follow. We expect that every Oxide employee has the capacity to lead others — and we tap this capacity frequently. Of course, a company in which everyone is trying to direct all traffic all the time would be a madhouse, so we also very much rely on following one another too! Just as our compensation model allows us to internalize the values of different roles, it allows us to appreciate the value of both leading and following, and empowers us each with the judgement to know when to do which. This isn’t always easy or free of ambiguity, but this particular dimension of our versatility has been essential — and our compensation model serves to encourage it. It causes us to hire carefully and deliberately. Of course, one should always hire carefully and deliberately, but this often isn’t the case — and many a startup has been ruined by reckless expansion of headcount. One of the roots of this can be found in a dirty open secret of Silicon Valley middle management: its ranks are taught to grade their career by the number of reports in their organization. Just as if you were to compensate software engineers based on the number of lines of code they wrote, this results in perverse incentives and predictable disasters — and any Silicon Valley vet will have plenty of horror stories of middle management jockeying for reqs or reorgs when they should have been focusing on product and customers. When you can eliminate middle management, you eliminate this incentive. We grow the team not because of someone’s animal urges to have the largest possible organization, but rather because we are at a point where adding people will allow us to better serve our market and customers. It liberates feedback from compensation. Feedback is, of course, very important: we all want to know when and where we’re doing the right thing! And of course, we want to know too where there is opportunity for improvement. However, Silicon Valley has historically tied feedback so tightly to compensation that it has ceased to even pretend to be constructive: if it needs to be said, performance review processes aren’t, in fact, about improving the performance of the team, but rather quantifying and stack-ranking that performance for purposes of compensation. When compensation is moved aside, there is a kind of liberation for feedback itself: because feedback is now entirely earnest, it can be expressed and received thoughtfully. It allows people to focus on doing the right thing. In a world of traditional, compensation-tied performance review, the organizational priority is around those things that affect compensation — even at the expense of activity that clearly benefits the company. This leads to all sorts of wild phenomena, and most technology workers will be able to tell stories of doing things that were clearly right for the company, but having to hide it from management that thought only narrowly in terms of their own stated KPIs and MBOs. By contrast, over and over (and over!) again, we have found that people do the right thing at Oxide — even if (especially if?) no one is looking. The beneficiary of that right thing? More often than not, it’s our customers, who have uniformly praised the team for going above and beyond. It allows us to focus on the work that matters. Relatedly, when compensation is non-uniform, the process to figure out (and maintain) that non-uniformity is laborious. All of that work — of line workers assembling packets explaining themselves, of managers arming themselves with those packets to fight in the arena of organizational combat, and then of those same packets ultimately being regurgitated back onto something called a review — is work. Assuming such a process is executed perfectly (something which I suppose is possible in the abstract, even though I personally have never seen it), this is work that does not in fact advance the mission of the company. Not having variable compensation gives us all of that time and energy back to do the actual work — the stuff that matters. It has stoked an extraordinary sense of teamwork. For me personally — and as I relayed on an episode of Software Misadventures — the highlights of my career have been being a part of an extraordinary team. The currency of a team is mutual trust, and while uniform compensation certainly isn’t the only way to achieve that trust, boy does it ever help! As Steve and I have told one another more times that we can count: we are so lucky to work on this team, with its extraordinary depth and breadth. While our findings have been very positive, I would still reiterate what we said four years ago: we don’t know what the future holds, and it’s easier to make an unwavering commitment to the transparency rather than the uniformity. That said, the uniformity has had so many positive ramifications that the model feels more important than ever. We are beyond the point of this being a curiosity; it’s been essential for building a mission-focused team taking on a problem larger than ourselves. So it’s not a fit for everyone — but if you are seeking an extraordinary team solving hard problems in service to customers, consider Oxide!

1st May 2025 42 votes
How Oxide Cuts Data Center Power Consumption in Half

Here’s a sobering thought: today, data centers already consume 1-2% of the world’s power, and that percentage will likely rise to 3-4% by the end of the decade. According to Goldman Sachs research, that rise will include a doubling in data center carbon dioxide emissions. As the data and AI boom progresses, this thirst for power shows no signs of slowing down anytime soon. Two key challenges quickly become evident for the 85% of IT that currently lives on-premises. How can organizations reduce power consumption and corresponding carbon emissions? How can organizations keep pace with AI innovation as existing data centers run out of available power? Figure 1. Masanet et al. (2020), Cisco, IEA, Goldman Sachs Research Rack-scale design is critical to improved data center efficiency Traditional data center IT consumes so much power because the fundamental unit of compute is an individual server; like a house where rooms were built one at a time, with each room having its own central AC unit, gas furnace, and electrical panel. Individual rackmount servers are stacked together, each with their own AC power supplies, cooling fans, and power management. They are then paired with storage appliances and network switches that communicate at arm’s length, not designed as a cohesive whole. This approach fundamentally limits organizations' ability to maintain sustainable, high-efficiency computing systems. Of course, hyperscale public cloud providers did not design their data center systems this way. Instead, they operate like a carefully planned smart home where everything is designed to work together cohesively and is operated by software that understands the home’s systems end-to-end. High-efficiency, rack-scale computers are deployed at scale and operate as a single unit with integrated storage and networking to support elastic cloud computing services. This modern archietecture is made available to the market as public cloud, but that rental-only model is ill-fit for many business needs. Compared to a popular rackmount server vendor, Oxide is able to fill our specialized racks with 32 AMD Milan sleds and highly-available network switches using less than 15kW per rack, doubling the compute density in a typical data center. With just 16 of the alternative 1U servers and equivalent network switches, over 16kW of power is required per rack, leading to only 1,024 CPU cores vs Oxide’s 2,048. Extracting more useful compute from each kW of power and square foot of data center space is key to the future effectiveness of on-premises computing. At Oxide, we’ve taken this lesson in advancing rack-scale design, improved upon it in several ways, and made it available for every organization to purchase and operate anywhere in the world without a tether back to the public cloud. Our Cloud Computer treats the entire rack as a single, unified computer rather than a collection of independent parts, achieving unprecedented power efficiency. By designing the hardware and software together, we’ve eliminated unnecessary components and optimized every aspect of system operation through a control plane with visibility to end-to-end operations. When we started Oxide, the DC bus bar stood as one of the most glaring differences between the rack-scale machines at the hyperscalers and the rack-and-stack servers that the rest of the market was stuck with. That a relatively simple piece of copper was unavailable to commercial buyers — despite being unequivocally the right way to build it! — represented everything wrong with the legacy approach. The bus bar in the Oxide Cloud Computer is not merely more efficient, it is a concrete embodiment of the tremendous gains from designing at rack-scale, and by integrating hardware with software. — Bryan Cantrill The improvements we’re seeing are rooted in technical innovation Replacing low-efficiency AC power supplies with a high-efficiency DC Bus Bar This eliminates the 70 total AC power supplies found in an equivalent legacy server rack within 32 servers, two top-of-rack switches, and one out-of-band switch, each with two AC power supplies. This power shelf also ensures the load is balanced across phases, something that’s impossible with traditional power distribution units found in legacy server racks. Bigger fans = bigger efficiency gains using 12x less energy than legacy servers, which each contain as many as 7 fans, which must work much harder to move air over system components. Purpose-built for power efficiency less restrictive airflow than legacy servers by eliminating extraneous components like PCIe risers, storage backplanes, and more. Legacy servers need many optional components like these because they could be used for any number of tasks, such as point-of-sale systems, data center servers, or network-attached-storage (NAS) systems. Still, they were never designed optimally for any one of those tasks. The Oxide Cloud Computer was designed from the ground up to be a rack-scale cloud computing powerhouse, and so it’s optimized for exactly that task. Hardware + Software designed together By designing the hardware and software together, we can make hardware choices like more intelligent DC-DC power converters that can provide rich telemetry to our control plane, enabling future feature enhancements such as dynamic power capping and efficiency-based workload placement that are impossible with legacy servers and software systems. Learn more about Oxide’s intelligent Power Shelf Controller The Bottom Line: Customers and the Environment Both Benefit Reducing data center power demands and achieving more useful computing per kilowatt requires fundamentally rethinking traditional data center utilization and compute design. At Oxide, we’ve proven that dramatic efficiency gains are possible when you rethink the computer at rack-scale with hardware and software designed thoughtfully and rigorously together. Ready to learn how your organization can achieve these results? Schedule time with our team here. Together, we can reclaim on-premises computing efficiency to achieve both business and sustainability goals.

8th Nov 2024 95 votes

More in programming

Abusing ID3 chapters to turn videos into glanceable podcasts

I listen to a lot of podcasts, and I like how they fit around other tasks. I press play, lock my phone, and put it down. I’m free to wash the dishes, fold the laundry, or shop for groceries. Unfortunately, more and more information is only published as a video. Technical talks, conference sessions, video essays – they don’t work in an audio-only podcast app. I could convert these videos to MP3 files, but that breaks down the moment a video isn’t pure spoken word. If a speaker says, “Look at this slide” or holds up a diagram, an audio-only file leaves me stranded. I don’t want to give up the podcast player I like, nor stare at a screen for an hour – but I do want the information in these videos. To solve this, I’m abusing my podcast player’s chapter support. This gives me the best of both worlds: I can listen to a video as audio-first, and glance at my lock screen if I need a moment of visual context. The idea: Chapters every few seconds MP3 files can have ID3 metadata, and ID3 metadata can include chapters. A chapter covers a particular time range, and it can have an associated title, description, and cover art. My podcast app of choice is Overcast, which can’t play videos, but it does have robust chapter support. I can jump between chapters, navigate a table of contents, and see per-chapter cover art. To get videos into Overcast, I’m creating MP3 files with a new chapter every few seconds, and the per-chapter cover art is a corresponding frame from the video. As I play the file, I get a slow, stop-motion-like rendition of the original video. If my phone is locked, I can glance at my lock screen and see the current frame in the Now Playing screen. Overcast is developed by Marco Arment, and I got this idea from Forecast, his app for adding chapters to podcasts. In particular, I was struck by its ability to create chapters that don’t display in the chapter list – ideal if I don’t want a table of contents with hundreds of entries. As I was developing my script, I compared my output to the output from Forecast to ensure I was creating the chapters correctly. The code: FFmpeg and Mutagen There are three steps in this process: Convert a video file to an MP3 Extract images from the video at a fixed interval Insert the images as hidden chapters in the MP3 file Let’s go through each in turn. 1. Convert a video file to an MP3 Converting a video file to an MP3 is a single FFmpeg command: ffmpeg -i video.mp4 audio.mp3 This is consistently the slowest step of the process, and I do wonder if I could use different settings or an alternative encoder to make it go faster – but it’s not slow enough to be worth further investigation. 2. Extract images from the video at a fixed interval Extracting images from a video needs a more complicated FFmpeg command: ffmpeg -i video.mp4 \ -vf 'fps=1/5,scale=iw*sar:ih,scale=min(iw\,945):min(ih\,945):force_original_aspect_ratio=decrease' \ thumbnail_%04d.jpg This extracts an image every 5 seconds, downscales any image larger than 945 pixels square (while preserving the original aspect ratio), and saves the results as sequentially numbered JPEG images (thumbnail_0001.png, thumbnail_0002.png, and so on). The key is the -vf flag, which defines two FFmpeg filters: The fps filter selects one frame every 5 seconds (fps=1/5). The first scale filter scales the width based on the sample aspect ratio (scale=iw*sar:ih). Without this filter, frames can be stretched and distorted. The second scale filter scales the input video, preserving the original aspect ratio (force_original_aspect_ratio=decrease), and ensuring the output images fit within 945×945px or the size of the input video, whichever is smaller. My limit is 945 pixels because that’s the largest size that cover art is shown on my iPhone. This filter still isn’t completely correct – it sometimes creates images from portrait videos that are smaller than I’m expecting – but it’s good enough. These are only thumbnails for glancing at, and if I want to change it later, I can always do the image resizing outside FFmpeg. 3. Insert the images as hidden chapters in the MP3 file Inserting the chapters into the MP3 file is more complicated. Although FFmpeg has basic support for ID3 metadata, as far as I know, it can’t insert chapters with per-chapter artwork. Instead, I’m going to reach for Python and the Mutagen library. Here’s the code to add a chapter to an MP3 file: from mutagen.id3 import APIC, CHAP, ID3, PictureType audio = ID3("audio.mp3") with open("thumbnail_0001.jpg", "rb") as f: img_data = f.read() image_frame = APIC(mime="image/jpeg", type=PictureType.OTHER, data=img_data) chapter_frame = CHAP( element_id="chp1", start_time=0, end_time=5 * 1000, sub_frames=[image_frame] ) audio.add(chapter_frame) audio.save() This creates a single chapter that lasts the first 5 seconds (0 to 5000 milliseconds), and the per-chapter cover art is thumbnail_0001.jpg. If we ran this in a loop, we could add images for every 5 second slice of the original video. This code is inserting two frames into the ID3 metadata: The CHAP (chapter) frame contains the timing information, and it can have subframes for metadata like title, chapter art, or associated URL. The APIC (attached picture) subframe contains information about a picture, which can either be a blob of image data or a URL to an image on the web. Normally, you’d also insert a CTOC frame which defines a table of contents, but I don’t want a TOC with hundreds of 5-second chapters, so I’m deliberately not doing this here. This is allowed by the ID3 spec – you’re not required to insert a CTOC frame if you’re using chapters, and you can have chapters that aren’t listed in your table of contents. To work out which frames I needed, I used Forecast to create some chapters by hand, and I inspected their frames. In particular, loading an MP3 and calling Mutagen’s pprint() method shows a human-readable list of frames, and then I could drill into the individual fields: from mutagen.id3 import ID3 audio = ID3("audio.mp3") print(audio.pprint()) I wrapped all this code in a project called glancecast, which allows you to convert a video file with a single command, with optional flags to set the frame length and chapter art size: $ python3 glancecast.py interesting_talk.mp4 interesting_talk.mp3 The process takes a minute or so to complete, most of which is spent transcoding the video file to MP3. The resulting MP3s are usually 40 to 50 MB in size, which is very reasonable. The outcome: How it looks in practice Here’s what one of these “glanceable” podcasts looks like in Overcast and on my lock screen: Maggie Appleton presented this talk over two years ago and it’s been on my “talks to watch” list ever since. Once I put it in Overcast? I listened to it in less than a day. It’s not a lot of extra information, but enough that I can quickly glance down and get the gist of what a speaker is saying. Both views update with a new frame every few seconds, or I can put my phone in my pocket and ignore the screen. I’ve used this approach for half a dozen videos so far, and I’m happy with the results. I expect to keep using it, because I have a long queue of videos I’ve been meaning to watch. If you’d like to try this, check out glancecast for the full code and instructions. [If the formatting of this post looks odd in your feed reader, visit the original article]

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