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• avcodec/libvpxenc : fix setting amount of threads used for encoding

  19 mai 2018, par James Almer

  avcodec/libvpxenc : fix setting amount of threads used for encoding
  The libvpx doxy says that a value of 0 for the g_threads field is
  
  equivalent to a value of 1, whereas for avctx->thread_count it means
  
  the maximum amount of threads possible for the host system.
  Use av_cpu_count() to get the correct thread count when auto threads
  
  is requested.
  Reviewed-by : James Zern <jzern@google.com>
  
  Signed-off-by : James Almer <jamrial@gmail.com>
  

  • [DH] libavcodec/libvpxenc.c

• Getting raw h264 packages from USB camera on Raspberry Pi

  13 juin 2018, par Aninano

  I am trying to receive H264 frames from a USB webcamera connected to my Raspberry PI

  Using the RPi Camera Module I can run the following command to get H264 data outputted in stdin : raspivid -t 0 -w 640 -h 320 -fps 15 -o - with close to zero latency

  Is there an equivalent function to do this with a USB camera ? I have two USB cameras I would like to do this with.

  Using ffprobe /dev/videoX I get the following output : (shorted down to the improtant details) :

  $ ffprobe /dev/video0
  
  ...
  
  Input #0, video4linux2,v4l2, from '/dev/video0':
  
  Duration: N/A, start: 18876.273861, bitrate: 147456 kb/s
  
  Stream #0:0: Video: rawvideo (YUY2 / 0x32595559), yuyv422, 1280x720, 147456 kb/s, 10 fps, 10 tbr, 1000k tbn, 1000k tbc
  
  
  
  $ ffprobe /dev/video1
  
  ...
  
  Input #0, video4linux2,v4l2, from '/dev/video1':
  
  Duration: N/A, start: 18980.783228, bitrate: 115200 kb/s
  
  Stream #0:0: Video: rawvideo (YUY2 / 0x32595559), yuyv422, 800x600, 115200 kb/s, 15 fps, 15 tbr, 1000k tbn, 1000k tbc
  
  
  
  
  
  $ ffprobe /dev/video2
  
  ...
  
  Input #0, video4linux2,v4l2, from '/dev/video2':
  
  Duration: N/A, start: 18998.984143, bitrate: N/A
  
  Stream #0:0: Video: h264 (Main), yuv420p(progressive), 1920x1080, -5 kb/s, 30 fps, 30 tbr, 1000k tbn, 2000k tbc

  As far as I can tell two of them are not H264, which will need to be "decoded" to H264 so I understand there is added a bit latency there. But the third one (video2) is H264 so I should be able to get data from it ? I’ve tried to just pipe it out with CAT but it says I got invalid arguments.

  I’ve come as far as using FFMPEG might be the only option here. Would like to use software easily available for all RPi (apt install).

  Bonus question regarding H264 packages : When I stream the data from raspivid command to my decoder it works perfectly. But if I decide to drop the 10 first packages then it never initializes the decoding process and just shows a black background. Anyone know what might be missing in the first packages that I might be able to recreate in my software so I dont have to restart the stream for every newly connected user ?

  EDIT : Bonus Question Answer : After googling around I see that the first two frames raspivid sends me are. So by ignoring the two first frames my decoder wont "decode" properly. So if I save those frames and send them first to all new users it works perfectly. Seems like these are used in some kind of initial process.

  0x27 = 01 00111 = type 7    Sequence parameter set (B-frame)
  
  0x28 = 01 01000 = type 8    Picture parameter set (B-frame)

• Getting raw h264 packets from USB camera on Raspberry Pi

  14 juin 2018, par Aninano

  I am trying to receive H264 frames from a USB webcamera connected to my Raspberry PI

  Using the RPi Camera Module I can run the following command to get H264 data outputted in stdin : raspivid -t 0 -w 640 -h 320 -fps 15 -o - with close to zero latency

  Is there an equivalent function to do this with a USB camera ? I have two USB cameras I would like to do this with.

  Using ffprobe /dev/videoX I get the following output : (shorted down to the important details) :

  $ ffprobe /dev/video0
  
  ...
  
  Input #0, video4linux2,v4l2, from '/dev/video0':
  
  Duration: N/A, start: 18876.273861, bitrate: 147456 kb/s
  
  Stream #0:0: Video: rawvideo (YUY2 / 0x32595559), yuyv422, 1280x720, 147456 kb/s, 10 fps, 10 tbr, 1000k tbn, 1000k tbc
  
  
  
  $ ffprobe /dev/video1
  
  ...
  
  Input #0, video4linux2,v4l2, from '/dev/video1':
  
  Duration: N/A, start: 18980.783228, bitrate: 115200 kb/s
  
  Stream #0:0: Video: rawvideo (YUY2 / 0x32595559), yuyv422, 800x600, 115200 kb/s, 15 fps, 15 tbr, 1000k tbn, 1000k tbc
  
  
  
  
  
  $ ffprobe /dev/video2
  
  ...
  
  Input #0, video4linux2,v4l2, from '/dev/video2':
  
  Duration: N/A, start: 18998.984143, bitrate: N/A
  
  Stream #0:0: Video: h264 (Main), yuv420p(progressive), 1920x1080, -5 kb/s, 30 fps, 30 tbr, 1000k tbn, 2000k tbc

  As far as I can tell two of them are not H264, which will need to be "decoded" to H264 so I understand there is added a bit latency there. But the third one (video2) is H264 so I should be able to get data from it ? I’ve tried to just pipe it out with CAT but it says I got invalid arguments.

  I’ve come as far as using FFMPEG might be the only option here. Would like to use software easily available for all RPi (apt install).

  Bonus question regarding H264 packets : When I stream the data from raspivid command to my decoder it works perfectly. But if I decide to drop the 10 first packets then it never initializes the decoding process and just shows a black background. Anyone know what might be missing in the first packets that I might be able to recreate in my software so I dont have to restart the stream for every newly connected user ?

  EDIT : Bonus Question Answer : After googling around I see that the first two frames raspivid sends me are. So by ignoring the two first frames my decoder wont "decode" properly. So if I save those frames and send them first to all new users it works perfectly. Seems like these are used in some kind of initial process.

  0x27 = 01 00111 = type 7    Sequence parameter set (B-frame)
  
  0x28 = 01 01000 = type 8    Picture parameter set (B-frame)