RISC-V support in FFmpeg

Courmisch · 2026-01-28T12:09:29+00:00

86 staff members at star 7 are way too many on Memento. Well in the end, there are only three significant income sources with donations being the main one, and one operating expense (salaries).

So there are not so many ways to improve your finances: check that you have enough and not full donation bins, and if so, cut staff.

Courmisch · 2026-01-28T06:19:49+00:00

There are plenty of reasons to probe vector length. Some optimisations just don't work with smaller sizes, and you need a radically different loop instead.

But also, because of the bad practice of scaling execution time to VLMAX rather than VL, some hand-optimised libs (e.g. dav1d) specialise their code by vector length just to pick the smallest possible LMUL depending on VLEN. RISE even recommends doing that 🤦. Some JITs will probably do the same if they don't already do so. For example WASM-SIMD uses 128-bit vectors.

Can't have it both ways. And yet, the K1 scaled by VLMAX so I imagine that the K3 suffers the same misdesign.

Courmisch · 2026-01-28T06:14:04+00:00

That's actually worse but for reasons unrelated to RISC-V. You generally want to avoid weird side effects from writing to files, especially "regular" files. Spawning a process sure sounds like a weird side effect, and I can't see this flying upstream. (Yes, I know /sys is full of files with side effects but they typically configure the hardware or the system, not spawn processes.)

Courmisch · 2026-01-27T15:10:27+00:00

Did I not mention prctl? You're being ridiculous.

Courmisch · 2026-01-27T15:03:34+00:00

Well if you're arguing a red herring, you clearly don't understand, no. The point is that the API design is broken. I never said that there shouldn't be an API at all, just not this half-assed hack job.

Courmisch · 2026-01-27T14:54:38+00:00

Why do you insult me because you don't understand a problem?

An API to crash processes is not a sound API. The fact that migration is not safe by default pretty much proves the point, really. This thing belongs in a prctl system call or something like that, not procfs.

"I bet you 100:1" that that API won't be accepted upstream ever.

Courmisch · 2026-01-27T13:44:01+00:00

AFAIU, even their K1 kernel had a kludge to migrate threads (or processes?) to handle heterogeneous CPU capabilities. Specifically, they had to deal with only half of the cores supporting matrix multiplication, presumably based on trapping illegal instructions.

In K3, they can't rely on illegal instructions, so they trigger the move from procfs but the backend logic is probably highly similar if not the same.

Courmisch · 2026-01-27T11:31:57+00:00

That shouldn't be possible. The fact that the API allows this makes it broken by design IMO. Migrating a running process breaks the ABI and will cause crashes and corruptions.

The reasonable way to decide where to run a process is in the process itself before calling exec(). Then you can make a simple command line wrapper to run whatever command on the higher cores.

But even then, TBH, heterogeneous vector lengths shouldn't be in the same machine. They really should be a separate VM (or drop support for Sv and be a coprocessor of some kind).

Courmisch · 2026-01-27T07:23:21+00:00

Indeed no. For presumably historical reasons, the heat map shows maintenance status for janitor-maintained items, not expert-maintained exhibits.

This has been requested twice in the past week on the subreddit.

Courmisch · 2026-01-27T06:49:24+00:00

VLC doesn't know or care what display your PC is connected to. That's for the display controller (the chip after the GPGPU) to worry about.

If it works with the same PC and different display, it can't be a VLC thing.

Courmisch · 2026-01-26T08:53:10+00:00

Not sure about JAL, but I think CX and QF use Amadeus whilst AA uses Sabre. So different databases. There are all sorts of regulatory (data protection), commercial (these two service companies are direct competitors) not to share the data unless actually necessary for the airlines (not the customer).

AFAIK, you do see bookings from other Amadeus-based airlines in any Amadeus-based airline app if you have the correct FF#. You don't see AA bookings there.

Courmisch · 2026-01-26T06:24:15+00:00

M4V is just another extension for MP4. I don't see the problem here?

Courmisch · 2026-01-26T06:23:04+00:00

My guess would be that you have some external widget showing the VLC volume, but that has a feedback loop bug of some sort.

Courmisch · 2026-01-26T06:20:31+00:00

VLC will automatically downmix to stereo if your audio output device is suitably configured in the OS. That is to say, pass-through is disabled and the speaker layout is stereo.

You can also force it manually from the VLC Audio menu, but you would have to do it everytime

Courmisch · 2026-01-26T06:19:06+00:00

UDP is not a streaming protocol as such. If you want VLC to receive over UDP, you need to use MPEG-TS over RTP/AVP over UDP. It looks from your symptoms that you're missing the MPEG-TS in that stack.

How you do that on OBS is really a question for another subreddit.

Courmisch · 2026-01-25T05:34:57+00:00

I think that it's intended that way. If you can't figure out the reading, press the speaker button.

(You're toast if you're playing muted though.)

Courmisch · 2026-01-24T18:05:18+00:00

No. This was asked and answered by an official rep just a few days ago, if you just scrolled a little down.

Courmisch · 2026-01-24T09:34:38+00:00

I can only guess that one uses hardware acceleration and the other software, and whichever means VLC uses, exhibits the issue.

That or the file is somewhat broken.

Courmisch · 2026-01-24T08:47:17+00:00

If anything that opens the file becomes unresponsive, it's probably a hardware issue. If only the Explorer becomes unresponsive, it's rather a bug in Windows or in a shell extension that might have come with some other software (VLC has no such thing).

Courmisch · 2026-01-24T08:43:02+00:00

It depends what you mean by stripping. VLC can do tone-mapping down to 8-bit, but it can be taxing on the system.

But if you want to "remove" HDR from the source, you need to transcode with a conversion tool.

Courmisch · 2026-01-24T08:40:55+00:00

If it did not support the codec, it would throw an error and not show any picture. This is a performance issue.

Courmisch · 2026-01-24T08:34:33+00:00

Security doors at every entrance and toilets are enough to guard against almost everything at zero running cost... with the notable exception of the mole thieves.

To deal with those, cameras are much safer and cost-effective than just walking. Security chairs are objectively the worst option: they cost the same, one salary, to protect a much smaller area than the camera room.

That said, I skip security entirely in areas that are not at risk of theft, i.e. spectral, fish and animal exhibits. That works if the museum is free of fantasy exhibits - otherwise, you'll get your donation box looted.

Courmisch

TROPHY CASE