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I've spent so much time trying to figure out how this FFMPEG and their libraries work :(

I have a RaspberryPi 2B and a Logitech USB Webcam. Here is the input from FFMPEG list from my /dev/video0:

    ffmpeg version 3.0.2-2~bpo8+1 Copyright (c) 2000-2016 the FFmpeg developers
  built with gcc 4.9.2 (Debian 4.9.2-10)
  configuration: --prefix=/usr --extra-version='2~bpo8+1' --toolchain=hardened --libdir=/usr/lib/arm-linux-gnueabihf --incdir=/usr/include/arm-linux-gnueabihf --cc=cc --cxx=g++ --enable-gpl --enable-shared --disable-stripping --disable-decoder=libopenjpeg --disable-decoder=libschroedinger --enable-avresample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmodplug --enable-libmp3lame --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-librubberband --enable-librtmp --enable-libschroedinger --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxvid --enable-libzvbi --enable-openal --enable-opengl --enable-x11grab --enable-libdc1394 --enable-libiec61883 --enable-libzmq --enable-frei0r --enable-chromaprint --enable-libx264
  libavutil      55. 17.103 / 55. 17.103
  libavcodec     57. 24.102 / 57. 24.102
  libavformat    57. 25.100 / 57. 25.100
  libavdevice    57.  0.101 / 57.  0.101
  libavfilter     6. 31.100 /  6. 31.100
  libavresample   3.  0.  0 /  3.  0.  0
  libswscale      4.  0.100 /  4.  0.100
  libswresample   2.  0.101 /  2.  0.101
  libpostproc    54.  0.100 / 54.  0.100
[video4linux2,v4l2 @ 0x1171bb0] Raw       :     yuyv422 :           YUYV 4:2:2 : 640x480 160x90 160x120 176x144 320x180 320x240 352x288 432x240 640x360 800x448 800x600 864x480 960x720 1024x576 1280x720 1600x896 1920x1080 2304x1296 2304x1536
[video4linux2,v4l2 @ 0x1171bb0] Compressed:        h264 :                H.264 : 640x480 160x90 160x120 176x144 320x180 320x240 352x288 432x240 640x360 800x448 800x600 864x480 960x720 1024x576 1280x720 1600x896 1920x1080
[video4linux2,v4l2 @ 0x1171bb0] Compressed:       mjpeg :          Motion-JPEG : 640x480 160x90 160x120 176x144 320x180 320x240 352x288 432x240 640x360 800x448 800x600 864x480 960x720 1024x576 1280x720 1600x896 1920x1080
/dev/video0: Immediate exit requested

and here is the audio input:

**** List of CAPTURE Hardware Devices ****
card 1: C920 [HD Pro Webcam C920], device 0: USB Audio [USB Audio]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

I've tried this common and basic ffmpeg routine:

ffmpeg -y -f alsa -i hw:1 -i /dev/video0 -t 10  out12.avi

and here is the output:

ffmpeg version 3.0.2-2~bpo8+1 Copyright (c) 2000-2016 the FFmpeg developers
  built with gcc 4.9.2 (Debian 4.9.2-10)
  configuration: --prefix=/usr --extra-version='2~bpo8+1' --toolchain=hardened --libdir=/usr/lib/arm-linux-gnueabihf --incdir=/usr/include/arm-linux-gnueabihf --cc=cc --cxx=g++ --enable-gpl --enable-shared --disable-stripping --disable-decoder=libopenjpeg --disable-decoder=libschroedinger --enable-avresample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmodplug --enable-libmp3lame --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-librubberband --enable-librtmp --enable-libschroedinger --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxvid --enable-libzvbi --enable-openal --enable-opengl --enable-x11grab --enable-libdc1394 --enable-libiec61883 --enable-libzmq --enable-frei0r --enable-chromaprint --enable-libx264
  libavutil      55. 17.103 / 55. 17.103
  libavcodec     57. 24.102 / 57. 24.102
  libavformat    57. 25.100 / 57. 25.100
  libavdevice    57.  0.101 / 57.  0.101
  libavfilter     6. 31.100 /  6. 31.100
  libavresample   3.  0.  0 /  3.  0.  0
  libswscale      4.  0.100 /  4.  0.100
  libswresample   2.  0.101 /  2.  0.101
  libpostproc    54.  0.100 / 54.  0.100
Guessed Channel Layout for  Input Stream #0.0 : stereo
Input #0, alsa, from 'hw:1':
  Duration: N/A, start: 1466107437.084808, bitrate: 1024 kb/s
    Stream #0:0: Audio: pcm_s16le, 32000 Hz, 2 channels, s16, 1024 kb/s
Input #1, video4linux2,v4l2, from '/dev/video0':
  Duration: N/A, start: 1578.347093, bitrate: 147456 kb/s
    Stream #1:0: Video: rawvideo (YUY2 / 0x32595559), yuyv422, 1280x720, 147456 kb/s, 10 fps, 10 tbr, 1000k tbn, 1000k tbc
Output #0, avi, to 'out12.avi':
  Metadata:
    ISFT            : Lavf57.25.100
    Stream #0:0: Video: mpeg4 (FMP4 / 0x34504D46), yuv420p, 1280x720, q=2-31, 200 kb/s, 10 fps, 10 tbn, 10 tbc
    Metadata:
      encoder         : Lavc57.24.102 mpeg4
    Side data:
      unknown side data type 10 (24 bytes)
    Stream #0:1: Audio: mp3 (libmp3lame) (U[0][0][0] / 0x0055), 32000 Hz, stereo, s16p
    Metadata:
      encoder         : Lavc57.24.102 libmp3lame
Stream mapping:
  Stream #1:0 -> #0:0 (rawvideo (native) -> mpeg4 (native))
  Stream #0:0 -> #0:1 (pcm_s16le (native) -> mp3 (libmp3lame))
Press [q] to stop, [?] for help
[alsa @ 0xe9ec10] Thread message queue blocking; consider raising the thread_queue_size option (current value: 8)
frame=    4 fps=0.0 q=2.0 size=     154kB time=00:00:00.40 bitrate=3152.5kbits/sframe=    8 fps=7.7 q=12.0 size=     261kB time=00:00:00.80 bitrate=2670.1kbits/frame=   13 fps=8.3 q=21.4 size=     303kB time=00:00:01.30 bitrate=1911.3kbits/frame=   18 fps=8.7 q=31.0 size=     349kB time=00:00:01.80 bitrate=1586.8kbits/frame=   23 fps=8.8 q=31.0 size=     393kB time=00:00:02.30 bitrate=1401.3kbits/frame=   28 fps=9.0 q=31.0 size=     428kB time=00:00:02.80 bitrate=1253.2kbits/frame=   34 fps=9.4 q=31.0 size=     463kB time=00:00:03.40 bitrate=1116.7kbits/frame=   38 fps=9.2 q=31.0 size=     494kB time=00:00:03.80 bitrate=1065.3kbits/frame=   43 fps=9.3 q=31.0 size=     520kB time=00:00:04.30 bitrate= 990.6kbits/frame=   49 fps=9.5 q=24.8 size=     557kB time=00:00:04.90 bitrate= 931.1kbits/frame=   55 fps=9.6 q=31.0 size=     593kB time=00:00:05.50 bitrate= 883.7kbits/frame=   61 fps=9.7 q=24.8 size=     631kB time=00:00:06.10 bitrate= 847.9kbits/frame=   67 fps=9.8 q=31.0 size=     670kB time=00:00:06.70 bitrate= 818.7kbits/frame=   72 fps=9.8 q=31.0 size=     696kB time=00:00:07.20 bitrate= 791.4kbits/frame=   78 fps=9.9 q=31.0 size=     727kB time=00:00:07.80 bitrate= 763.8kbits/frame=   83 fps=9.9 q=31.0 size=     760kB time=00:00:08.30 bitrate= 750.1kbits/frame=   88 fps=9.8 q=31.0 size=     801kB time=00:00:08.80 bitrate= 745.4kbits/frame=   93 fps=9.8 q=31.0 size=     840kB time=00:00:09.30 bitrate= 740.1kbits/frame=   98 fps=9.8 q=31.0 size=     874kB time=00:00:09.80 bitrate= 730.4kbits/frame=  100 fps=9.7 q=31.0 Lsize=     890kB time=00:00:10.04 bitrate= 725.9kbits/s speed=0.979x    
video:757kB audio:114kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 2.143680%

The output seems fine, but the quality is poor, it's recording at 640x480.

Then, I tried this:

ffmpeg -f alsa -i hw:1 -vcodec h264 -f v4l2 -i /dev/video0 -vcodec copy -y -t 10 out4.mkv

The image is wonderful, but, unfortunately, the audio is recorded with a bit lag :(

All I want is to set the RaspberryPi to record a few seconds with the audio encompassed at the highest resolution possible, or at least some guidance to achieve that.

Many thanks!

  • I haven't tried it with audio since I'm using the micless raspicam, but IMO ffmpeg is just a vastly overrated waste of time -- look into uv4l instead (looks to me like that's what ffmpeg is using for the video source anyway). No fuss, no latency, max resolution & framerate, low processor usage, streaming web server, etc. – goldilocks Jun 16 '16 at 20:43
  • Thanks @goldilocks , but what about including audio... I mean, I tried OpenCV, but don't support audio+video. – juasmilla Jun 16 '16 at 20:46
  • As far as I can tell by searching online, uv4l does support audio (it began as a support for "linux TV" which I'm guessing means it is a major component in a lot of set-top cable boxes). The easiest format w/ raspicam was mjpeg, (which is, e.g., supported by most web browsers), and I believe that can include audio. – goldilocks Jun 16 '16 at 20:50
  • Cool, then, I'll have a try to that uv4l. Thanks again @goldilocks ! – juasmilla Jun 16 '16 at 20:53
  • I meant to leave an answer here demonstrating uv4l and didn't find time, but I just left one here; you'll have to adapt that to your context. An issue, I think: You may have to read from /dev/uv4l so whether you can get a output format which can be read streamwise that way with sound I don't know. The web server, BTW, is enabled by default and if you have nothing on port 8080 that's where you'll find it (there's an ugly front page, the stream is /stream or the middle button top row -- dunno if you can make use of that for openCV). – goldilocks Jun 25 '16 at 13:51

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