Opened 3 years ago
Last modified 3 years ago
#7596 new enhancement
ffmpeg ignores v4l2 device prefs and selects a non-optimal format
Reported by: | Cole Mickens | Owned by: | |
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Priority: | wish | Component: | avdevice |
Version: | unspecified | Keywords: | v4l2 |
Cc: | Blocked By: | ||
Blocking: | Reproduced by developer: | no | |
Analyzed by developer: | no |
Description
Summary:
- Set a v4l2 format preference.
- Use ffmpeg or mpv to open the v4l2 device.
- ffmpeg will use the correct resolution, but incorrect pixelformat
This results in a sub-optimal format being used, resulting in potentially highly unfortunate end-results for the user.
Ideally:
- ffmpeg would respect the preferences set for the device in v4l2
- ffmpeg would choose the more optimal resolution/format for the best result
In my case, since ffmpeg respects the resolution, but not the pixelformat, it winds up operating at the best 1080p YUYV profile, which is 5FPS. (compare to 1080p MJPEG which is 30FPS).
$ v4l2-ctl -d 4 --set-fmt-video=width=1920,height=1080,pixelformat=1 $ v4l2-ctl -d 4 --get-fmt-video Format Video Capture: Width/Height : 1920/1080 Pixel Format : 'MJPG' (Motion-JPEG) Field : None Bytes per Line : 0 Size Image : 4147200 Colorspace : sRGB Transfer Function : Default (maps to sRGB) YCbCr/HSV Encoding: Default (maps to ITU-R 601) Quantization : Default (maps to Full Range) Flags : $ mpv av://v4l2:/dev/video4 Playing: av://v4l2:/dev/video4 (+) Video --vid=1 (rawvideo 1920x1080 5.000fps) [autoconvert] Converting yuyv422 -> yuv422p VO: [gpu] 1920x1080 yuv422p V: 00:00:02 / 00:00:03 (87%) $ ffmpeg -f v4l2 -i /dev/video4 -c:v copy out.mkv ... Input #0, video4linux2,v4l2, from '/dev/video4': Duration: N/A, start: 23757.859585, bitrate: 165888 kb/s Stream #0:0: Video: rawvideo (YUY2 / 0x32595559), yuyv422, 1920x1080, 165888 kb/s, 5 fps, 5 tbr, 1000k tbn, 1000k tbc ... $ ffmpeg -f v4l2 -input_format mjpeg -i /dev/video4 -c:v copy out.mkv Input #0, video4linux2,v4l2, from '/dev/video4': Duration: N/A, start: 23792.047911, bitrate: N/A Stream #0:0: Video: mjpeg, yuvj422p(pc, bt470bg/unknown/unknown), 1920x1080, 30 fps, 30 tbr, 1000k tbn, 1000k tbc
Change History (1)
comment:1 by , 3 years ago
Component: | undetermined → avdevice |
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Keywords: | v4l2 added |
Priority: | normal → wish |
Type: | defect → enhancement |
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