Opened 6 years ago
Last modified 22 months ago
#7596 new enhancement
ffmpeg ignores v4l2 device prefs and selects a non-optimal format
| Reported by: | Cole Mickens | Owned by: | |
|---|---|---|---|
| Priority: | wish | Component: | avdevice |
| Version: | git-master | Keywords: | v4l2 |
| Cc: | leezu | 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 (3)
comment:1 by , 6 years ago
| Component: | undetermined → avdevice |
|---|---|
| Keywords: | v4l2 added |
| Priority: | normal → wish |
| Type: | defect → enhancement |
comment:2 by , 2 years ago
| Cc: | added |
|---|---|
| Version: | unspecified → git-master |
Reproduced on git master
% v4l2-ctl -d 0 --get-fmt-video ~/Downloads
Format Video Capture:
Width/Height : 1280/720
Pixel Format : 'YUYV' (YUYV 4:2:2)
Field : None
Bytes per Line : 2560
Size Image : 1843200
Colorspace : sRGB
Transfer Function : Rec. 709
YCbCr/HSV Encoding: ITU-R 601
Quantization : Default (maps to Limited Range)
Flags :
% v4l2-ctl --list-formats-ext --device /dev/video0 ~/Downloads
ioctl: VIDIOC_ENUM_FMT
Type: Video Capture
[0]: 'MJPG' (Motion-JPEG, compressed)
Size: Discrete 1280x720
Interval: Discrete 0.033s (30.000 fps)
Size: Discrete 320x240
Interval: Discrete 0.033s (30.000 fps)
Size: Discrete 640x360
Interval: Discrete 0.033s (30.000 fps)
Size: Discrete 640x480
Interval: Discrete 0.033s (30.000 fps)
[1]: 'YUYV' (YUYV 4:2:2)
Size: Discrete 1280x720
Interval: Discrete 0.100s (10.000 fps)
Size: Discrete 320x240
Interval: Discrete 0.033s (30.000 fps)
Size: Discrete 640x360
Interval: Discrete 0.033s (30.000 fps)
Size: Discrete 640x480
Interval: Discrete 0.033s (30.000 fps)
% v4l2-ctl -d 0 --set-fmt-video=width=1280,height=720,pixelformat=MJPG ~/Downloads
% v4l2-ctl -d 0 --get-fmt-video ~/Downloads
Format Video Capture:
Width/Height : 1280/720
Pixel Format : 'MJPG' (Motion-JPEG)
Field : None
Bytes per Line : 0
Size Image : 1843200
Colorspace : sRGB
Transfer Function : Rec. 709
YCbCr/HSV Encoding: ITU-R 601
Quantization : Default (maps to Full Range)
Flags :
% ~/Downloads/ffmpeg -v 9 -loglevel 99 -i /dev/video0 -input_format mjpeg ~/Downloads
ffmpeg version N-107804-gaa9eabb7a5-https://www.martin-riedl.de Copyright (c) 2000-2022 the FFmpeg developers
built with gcc 8 (Debian 8.3.0-6)
configuration: --prefix=/home/ffmpegBuild/out --enable-gpl --pkg-config-flags=--static --extra-version='https://www.martin-riedl.de' --enable-gray --enable-libxml2 --enable-libfreetype --enable-fontconfig --enable-libbluray --enable-libass --enable-libaom --enable-libopenh264 --enable-libsvtav1 --enable-libvpx --enable-libx264 --enable-libx265 --enable-libmp3lame --enable-libopus --enable-libvorbis
libavutil 57. 33.101 / 57. 33.101
libavcodec 59. 42.101 / 59. 42.101
libavformat 59. 30.100 / 59. 30.100
libavdevice 59. 8.101 / 59. 8.101
libavfilter 8. 46.103 / 8. 46.103
libswscale 6. 8.102 / 6. 8.102
libswresample 4. 8.100 / 4. 8.100
libpostproc 56. 7.100 / 56. 7.100
Splitting the commandline.
Reading option '-v' ... matched as option 'v' (set logging level) with argument '9'.
Reading option '-loglevel' ... matched as option 'loglevel' (set logging level) with argument '99'.
Reading option '-i' ... matched as input url with argument '/dev/video0'.
Reading option '-input_format' ... matched as AVOption 'input_format' with argument 'mjpeg'.
Trailing option(s) found in the command: may be ignored.
Finished splitting the commandline.
Parsing a group of options: global .
Applying option v (set logging level) with argument 9.
Successfully parsed a group of options.
Parsing a group of options: input url /dev/video0.
Successfully parsed a group of options.
Opening an input file: /dev/video0.
Probing video4linux2,v4l2 score:99 size:0
[video4linux2,v4l2 @ 0x5e06df3060] fd:3 capabilities:84a00001
[video4linux2,v4l2 @ 0x5e06df3060] Current input_channel: 0, input_name: Camera 1, input_std: 0
[video4linux2,v4l2 @ 0x5e06df3060] Querying the device for the current frame size
[video4linux2,v4l2 @ 0x5e06df3060] Setting frame size to 1280x720
[video4linux2,v4l2 @ 0x5e06df3060] The V4L2 driver changed the pixel format from 0x32315559 to 0x47504A4D
[video4linux2,v4l2 @ 0x5e06df3060] Trying to set codec:rawvideo pix_fmt:yuv420p
[video4linux2,v4l2 @ 0x5e06df3060] The V4L2 driver changed the pixel format from 0x32315559 to 0x47504A4D
[video4linux2,v4l2 @ 0x5e06df3060] Trying to set codec:rawvideo pix_fmt:yuv420p
[video4linux2,v4l2 @ 0x5e06df3060] The V4L2 driver changed the pixel format from 0x32315659 to 0x47504A4D
[video4linux2,v4l2 @ 0x5e06df3060] Trying to set codec:rawvideo pix_fmt:yuv422p
[video4linux2,v4l2 @ 0x5e06df3060] The V4L2 driver changed the pixel format from 0x50323234 to 0x47504A4D
[video4linux2,v4l2 @ 0x5e06df3060] Trying to set codec:rawvideo pix_fmt:yuyv422
[video4linux2,v4l2 @ 0x5e06df3060] All info found
[video4linux2,v4l2 @ 0x5e06df3060] stream 0: start_time: 1491.3 duration: NOPTS
[video4linux2,v4l2 @ 0x5e06df3060] format: start_time: 1491.3 duration: NOPTS (estimate from bit rate) bitrate=147456 kb/s
Input #0, video4linux2,v4l2, from '/dev/video0':
Duration: N/A, start: 1491.299662, bitrate: 147456 kb/s
Stream #0:0, 1, 1/1000000: Video: rawvideo, 1 reference frame (YUY2 / 0x32595559), yuyv422, 1280x720, 0/1, 147456 kb/s, 10 fps, 10 tbr, 1000k tbn
Successfully opened the file.
At least one output file must be specified
[video4linux2,v4l2 @ 0x5e06df3060] Some buffers are still owned by the caller on close.
ioctl(VIDIOC_QBUF): Bad file descriptor
This issue is related to https://trac.ffmpeg.org/ticket/9878 which tracks ffmpeg ignored input_format specification (not just the defaults as in the current issue)
comment:3 by , 22 months ago
Looks at libavcodec/raw.c
What happend in avcodec_pix_fmt_to_codec_tag() ?
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