[FFmpeg-trac] #2882(undetermined:open): ffmpeg can't save h264 stream from v4l2 webcam into file without recoding

[FFmpeg]

#2882: ffmpeg can't save h264 stream from v4l2 webcam into file without recoding
-------------------------------------+-------------------------------------
             Reporter:  pchel        |                    Owner:
                 Type:  defect       |                   Status:  open
             Priority:  normal       |                Component:
              Version:  git-master   |  undetermined
             Keywords:  v4l2 h264    |               Resolution:
             Blocking:               |               Blocked By:
Analyzed by developer:  0            |  Reproduced by developer:  0
-------------------------------------+-------------------------------------

Comment (by pchel):

 Replying to [comment:10 xlinkz0]:
 > Does the webcam specification say that it can stream yuvj420p ?

 I can't find the webcam specification, but I'm pretty sure it supports

 Proofs
 {{{
 v4l2-ctl -i /dev/video0 --list-formats
 Video input set to 0 (Camera 1: ok)
 ioctl: VIDIOC_ENUM_FMT
         Index       : 0
         Type        : Video Capture
         Pixel Format: 'YUYV'
         Name        : YUV 4:2:2 (YUYV)

         Index       : 1
         Type        : Video Capture
         Pixel Format: 'H264' (compressed)
         Name        : H.264

         Index       : 2
         Type        : Video Capture
         Pixel Format: 'MJPG' (compressed)
         Name        : MJPEG
 }}}

 ffmpeg works just fine with yuvj420p and recoding


 > As far as I understand you are setting the option on the input. I do not
 think you can just request a different stream like that from a device.

 Don't understand that. I can request YUYV (5 frames per second), MJPEG (5
 frames per second if I'm right) and H264 (30 frames per second). I chose
 H264 because it gives me 30 fps from me webcam

 > You modified the simple command I gave you, does the simple command
 work?
 It doesn't. See below:
 {{{
 ➜  ffmpeg git:(master) ✗ ./ffmpeg -report -y -i /dev/video0 -t 10 -c copy
 out.mkv
 ffmpeg started on 2013-08-21 at 19:38:47
 Report written to "ffmpeg-20130821-193847.log"
 ffmpeg version N-55607-g2c1a215 Copyright (c) 2000-2013 the FFmpeg
 developers
   built on Aug 18 2013 10:35:18 with gcc 4.7 (Ubuntu/Linaro
 4.7.2-2ubuntu1)
   configuration: --enable-indev=alsa
   libavutil      52. 42.100 / 52. 42.100
   libavcodec     55. 28.100 / 55. 28.100
   libavformat    55. 13.103 / 55. 13.103
   libavdevice    55.  3.100 / 55.  3.100
   libavfilter     3. 82.100 /  3. 82.100
   libswscale      2.  5.100 /  2.  5.100
   libswresample   0. 17.103 /  0. 17.103
 /dev/video0: Invalid argument
 }}}

 > Are you only dissatisfied that it is not the proper format?

 The camera supports hardware h.264 encoding. I want to use this hardware
 capability.

 > If so you might want to reconsider transcoding it on the fly with a fast
 x264 preset that will work in real time for most mid-range processors.

 I've already have fast recoding from h.264 from camera into mp4 with
 command line
 {{{
 ffmpeg -f alsa -ac 2 -i plughw:CARD=C920,DEV=0 -acodec aac -vcodec h264 -f
 v4l2 -i /dev/video0 -q 0 -vcodec mpeg4  -y -strict -2 out.mp4
 }}}

 > Unless you can prove that you can receive in any other way a yuvj420p
 directly from the webcam without any software transcoding try :
 >
 > {{{
 > ffmpeg -y -i /dev/video0 -f v4l2 -c:v libx264 -preset superfast out.mkv
 > }}}

 It doesn't work again:
 {{{
 ➜  ffmpeg git:(master) ✗ ./ffmpeg -y -i /dev/video0 -f v4l2 -c:v libx264
 -preset superfast out.mkv
 ffmpeg version N-55607-g2c1a215 Copyright (c) 2000-2013 the FFmpeg
 developers
   built on Aug 18 2013 10:35:18 with gcc 4.7 (Ubuntu/Linaro
 4.7.2-2ubuntu1)
   configuration: --enable-indev=alsa
   libavutil      52. 42.100 / 52. 42.100
   libavcodec     55. 28.100 / 55. 28.100
   libavformat    55. 13.103 / 55. 13.103
   libavdevice    55.  3.100 / 55.  3.100
   libavfilter     3. 82.100 /  3. 82.100
   libswscale      2.  5.100 /  2.  5.100
   libswresample   0. 17.103 /  0. 17.103
 Unrecognized option 'preset'.
 Error splitting the argument list: Option not found
 }}}

 I suspect you need to put '-i' option between input and output params.


 In any case, thank you for your try to help me.

-- 
Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/2882#comment:14>
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