Playing from Capture Card or Webcam, Video device not found even though listed

[justin-pierce]

Important Information

Provide following Information:

• mpv 0.33.1
• macOS 11.1
• Source of the mpv binary or bundle: macOS builds by stolendata
• If known which version of mpv introduced the problem: unknown

Reproduction steps

Run in terminal:

mpv av://avfoundation:video="HD Pro Webcam C920"

"HD Pro Webcam C920" is derived from

ffmpeg -f avfoundation -list_devices true -i ""

Also tried ShadowCast (capture card), same thing. Goal is to achieve this on MacOS.

Expected behavior

mpv opens with view of webcam feed

Actual behavior

[ffmpeg] AVFoundation indev: Video device not found
[lavf] avformat_open_input() failed
Failed to recognize file format.

Log file

output.txt

When I try to capture the feed directly in ffmpeg, I have to specify a framerate -- is there a way to do that in mpv? The fps flag didn't seem to work -- thinking maybe it instead needs to be in the ffmpeg args?

[Akemi]

you can try av://avfoundation:0:none, eg instead of using the name using the index. the :none is to select no audio device.

you can specify various demuxer properties via demuxer-lavf-o, some examples:

--demuxer-lavf-o=video_size=1920x1080 
--demuxer-lavf-o=pixel_format=uyvy420
--demuxer-lavf-o=framerate=23.976

[justin-pierce]

Removing the video/audio tags seems to help, along with specifying framerate.

V: 00:00:09 / 00:00:10 (97%)
[lavf] error reading packet: Resource temporarily unavailable.
[lavf] error reading packet: Resource temporarily unavailable.
[lavf] error reading packet: Resource temporarily unavailable.
[lavf] error reading packet: Resource temporarily unavailable.
[lavf] error reading packet: Resource temporarily unavailable.
[lavf] error reading packet: Resource temporarily unavailable.
[lavf] error reading packet: Resource temporarily unavailable.
[lavf] error reading packet: Resource temporarily unavailable.
[lavf] error reading packet: Resource temporarily unavailable.
[lavf] error reading packet: Resource temporarily unavailable.
[lavf] error reading packet: Resource temporarily unavailable.
[lavf] ...treating it as fatal error.

Runs for a split second and then closes.

demuxer-force-retry-on-eof=yes

Keeps it going, though choppy and randomly drops later. Will keep playing with options. Thanks!

[m-sifi]

I've had more luck piping through FFmpeg to MPV then using MPV directly, however latency is slightly worse than Genki Arcade itself

ffmpeg -f avfoundation \
    -video_size 1280x720 -framerate 60 -pix_fmt yuyv422 -i "ShadowCast" \
    -vcodec libx264 -preset ultrafast -tune zerolatency \
    -f mpegts - | mpv -profile=low-latency -untimed -

[ctsrc]

Thank you @m-sifi and @justin-pierce.

Earlier today I was using Photo Booth on my MacBook Pro M1 2020 as a way of displaying the output of the "FaceTime HD Camera" built-in web camera of the machine to someone, so that they could see how they were sitting while we were shooting a video using a separate camera not connected to said machine. However, after about 4 or 5 minutes of not interacting with the machine, Photo Booth will pause and turn off the FaceTime HD Camera since it's not being used for recording. Presumably to conserve battery power.

So now this evening I decided that maybe we can use mpv instead of Photo Booth, if we want to use the FaceTime HD Camera that same way again in the future, and that's how I came across this GitHub issue and comments (it was among the first results on Google for mpv macos webcam source). Alternatively, we may just find a regular old mirror or other reflective surface and use that instead of using a computer and web camera for that purpose next time :P

Here is the command-line from m-sifi's comment but adjusted for ffmpeg v4.4 and using the FaceTime HD Camera of the MacBook Pro M1 2020 as input. It's only a couple of trivial differences, but I figured it might be useful to someone in the future if they too come across these comments from some search on Google and they just want to copy-paste something quickly in order to get on with whatever they were doing.

ffmpeg -f avfoundation \
    -video_size 1280x720 -framerate 30 -pixel_format yuyv422 -i "FaceTime HD Camera" \
    -vcodec libx264 -preset ultrafast -tune zerolatency \
    -f mpegts - | mpv -profile=low-latency -untimed -

PS: According to ffmpeg demuxer output on my MacBook Pro M1 2020 running macOS Big Sur 11.6, the FaceTime HD Camera of said machine through avfoundation supports the following modes:

• 1280x720@[1.000000 30.000000]fps
• 640x480@[1.000000 30.000000]fps

and the following pixel formats:

• uyvy422
• yuyv422
• nv12
• 0rgb
• bgr0

[ikester]

I'm having the same [lavf] error reading packet: Resource temporarily unavailable. issue as @justin-pierce using the latest brew build. It does work piping it in from ffmpeg, but I'd rather open it directly from mpv to avoid the reencoding.

Has anybody gotten mpv on the Mac to open a webcam stream directly? I have a feeling I may just be missing a parameter somewhere. Here's my command line on an M1 Max MacBook Pro:

mpv --demuxer-lavf-o=video_size=1920x1080,framerate=30,pixel_format=uyvy422 av://avfoundation:0:none                 ✔
[ffmpeg/demuxer] avfoundation: Stream #0: not enough frames to estimate rate; consider increasing probesize
 (+) Video --vid=1 (rawvideo 1920x1080)
[lavf] error reading packet: Resource temporarily unavailable.
[lavf] error reading packet: Resource temporarily unavailable.
[lavf] error reading packet: Resource temporarily unavailable.
[lavf] error reading packet: Resource temporarily unavailable.
[lavf] error reading packet: Resource temporarily unavailable.
[lavf] error reading packet: Resource temporarily unavailable.
[lavf] error reading packet: Resource temporarily unavailable.
[lavf] error reading packet: Resource temporarily unavailable.
[lavf] error reading packet: Resource temporarily unavailable.
[lavf] error reading packet: Resource temporarily unavailable.
[lavf] error reading packet: Resource temporarily unavailable.
[lavf] ...treating it as fatal error.
VO: [libmpv] 1920x1080 uyvy422
V: 00:00:00 / 00:00:00 (0%)

Exiting... (End of file)

mpv --version                                                                                                        ✔
mpv 0.34.1 Copyright © 2000-2021 mpv/MPlayer/mplayer2 projects
 built on Wed Aug 31 13:00:56 UTC 2022
FFmpeg library versions:
   libavutil       57.28.100
   libavcodec      59.37.100
   libavformat     59.27.100
   libswscale      6.7.100
   libavfilter     8.44.100
   libswresample   4.7.100
FFmpeg version: 5.1.2

[emilyst]

I've been trying for several days to see if I can get this to work. I have found this issue also occurs in IINA (obviously) but also even VLC and a few other media applications. It's as if they know how to grab the first available frame, but then something happens and they can't fetch the rest.

Based on "Resource temporarily unavailable" it seems as if libavformat is hitting an EAGAIN error reading the packets because it's requesting a non-blocking read from a device which necessarily blocks.

[ikester]

Based on "Resource temporarily unavailable" it seems as if libavformat is hitting an EAGAIN error reading the packets because it's requesting a non-blocking read from a device which necessarily blocks.

That's interesting. I don't know enough about libavformat but I would imagine ffmpeg would use the same call path. So it's puzzling that opening the stream with ffmpeg like it was suggested above does work. For example, this works for me with the MBP FaceTime camera:

ffmpeg -f avfoundation -video_size 1920x1080 -framerate 30 -pixel_format uyvy422 -i "0:none" -f matroska \
 - | mpv -profile=low-latency --untimed --fs -

[emilyst]

Based on "Resource temporarily unavailable" it seems as if libavformat is hitting an EAGAIN error reading the packets because it's requesting a non-blocking read from a device which necessarily blocks.

That's interesting. I don't know enough about libavformat but I would imagine ffmpeg would use the same call path. So it's puzzling that opening the stream with ffmpeg like it was suggested above does work. For example, this works for me with the MBP FaceTime camera:

ffmpeg -f avfoundation -video_size 1920x1080 -framerate 30 -pixel_format uyvy422 -i "0:none" -f matroska \
 - | mpv -profile=low-latency --untimed --fs -

Yeah, I agree it’s a bit odd. But ffmpeg seems to struggle to capture the stream smoothly as well. I would almost guess it’s just opening and closing the stream repeatedly, based on how the picture and audio stutter when I try it.

[ikester]

Based on "Resource temporarily unavailable" it seems as if libavformat is hitting an EAGAIN error reading the packets because it's requesting a non-blocking read from a device which necessarily blocks.

That's interesting. I don't know enough about libavformat but I would imagine ffmpeg would use the same call path. So it's puzzling that opening the stream with ffmpeg like it was suggested above does work. For example, this works for me with the MBP FaceTime camera:

ffmpeg -f avfoundation -video_size 1920x1080 -framerate 30 -pixel_format uyvy422 -i "0:none" -f matroska \
 - | mpv -profile=low-latency --untimed --fs -

Yeah, I agree it’s a bit odd. But ffmpeg seems to struggle to capture the stream smoothly as well. I would almost guess it’s just opening and closing the stream repeatedly, based on how the picture and audio stutter when I try it.

I don't see ffmpeg struggle on a MacBook Pro M1 Max, admittedly one of their higher end machines. It only slows down for me (drops frames, lags) when I add non-accelerated filters to the pipeline, which is what I'm trying to use it for.

In any event, I would love to find out why mpv is hitting the EAGAIN error when ffmpeg doesn't. Or if fmpeg does get it, how does it manage to ignore it or recover from it.

[maxexcloo]

Did anyone work this out? I'm having trouble with playing the stream with MPV also...