Recherche avancée

Sur d’autres sites (8772)

• how to generate rtsp stream using laptop cam [closed]

  13 décembre 2023, par Mubahsir

  I am using the following command to capture video from the laptop camera and stream it as an RTSP using ffmpeg :

  


  ffmpeg -f v4l2 -i /dev/video0 -c:v libx264 -profile:v baseline -pix_fmt yuv420p -b:v 500k -r 30 -f rtsp rtsp://127.0.0.1:1234


  


  Upon executing this command, the laptop camera's indicator light turns on, indicating that it is in use. However, when attempting to view the RTSP stream on VLC using the URL rtsp://127.0.0.1:1234, no video is displayed.

  


• FFmpeg/Libav audio decode example

  19 mai 2015, par Walid Baccari

  I am trying to get the same output as that of ffmpeg/avconv from converting an MP2 file to raw PCM using code. I used the audio_decode_example function from the tutorial included in the FFmpeg/Libav documentation but the outputs were different.

  What steps does the ffmpeg/avconv command perform that I need to add to my program to get the same output ?

  Edit :
  This is the output from avconv -v debug -i test.mp2 test.sw :

  avconv version v10_beta1-302-g606cc8a, Copyright (c) 2000-2014 the Libav developers
  
  built on Mar 20 2014 20:28:32 with gcc 4.8 (Ubuntu/Linaro 4.8.1-10ubuntu9)
  
  configuration: 
  
  libavutil     53.  6. 0 / 53.  6. 0
  
  libavcodec    55. 34. 1 / 55. 34. 1
  
  libavformat   55. 12. 0 / 55. 12. 0
  
  libavdevice   54.  0. 0 / 54.  0. 0
  
  libavfilter    4.  3. 0 /  4.  3. 0
  
  libavresample  1.  2. 0 /  1.  2. 0
  
  libswscale     2.  1. 2 /  2.  1. 2
  
  Splitting the commandline.
  
  Reading option '-v' ... matched as option 'v' (set libav* logging level) with argument 'debug'.
  
  Reading option '-i' ... matched as input file with argument 'test.mp2'.
  
  Reading option 'test1.sw' ... matched as output file.                                  
  
  Finished splitting the commandline.                                       
  
  Parsing a group of options: global .                
  
  Applying option v (set libav* logging level) with argument debug.
  
  Successfully parsed a group of options.
  
  Parsing a group of options: input file test.mp2.
  
  Successfully parsed a group of options.
  
  Opening an input file: test.mp2.
  
  [mp3 @ 0x27e5060] Probed with size=2048 and score=51
  
  [mp3 @ 0x27e5060] Estimating duration from bitrate, this may be inaccurate
  
  Guessed Channel Layout for  Input Stream #0.0 : stereo
  
  Input #0, mp3, from 'test.mp2':
  
    Duration: 00:00:04.80, start: 0.000000, bitrate: 64 kb/s
  
      Stream #0.0, 200, 1/14112000: Audio: mp2, 48000 Hz, stereo, s16p, 64 kb/s
  
  Successfully opened the file.
  
  Parsing a group of options: output file test1.sw.
  
  Successfully parsed a group of options.
  
  Opening an output file: test1.sw.
  
  Successfully opened the file.
  
  Detected 2 logical cores.
  
  [abuffer @ 0x27e5860] tb:1/48000 samplefmt:s16p samplerate: 48000 ch layout:0x3
  
  [abuffersink @ 0x2807040] auto-inserting filter 'auto-inserted fifo 0' between the filter 'audio format for output stream 0:0' and the filter 'output stream 0:0'
  
  [aformat @ 0x2806bc0] auto-inserting filter 'auto-inserted resampler 0' between the filter 'Parsed filter 0 anull' and the filter 'audio format for output stream 0:0'
  
  [AVAudioResampleContext @ 0x28092a0] audio_convert: found function: s16p to s16  (C)
  
  [AVAudioResampleContext @ 0x28092a0] audio_convert: found function: s16p to s16  (SSE2)
  
  [resample @ 0x2808560] fmt:s16p srate:48000 cl:stereo -> fmt:s16 srate:48000 cl:stereo
  
  Output #0, s16le, to 'test1.sw':
  
    Metadata:
  
      encoder         : Lavf55.12.0
  
      Stream #0.0, 0, 1/90000: Audio: pcm_s16le, 48000 Hz, stereo, s16, 1536 kb/s
  
    Stream mapping:
  
      Stream #0:0 -> #0:0 (mp2 -> pcm_s16le)
  
  Press ctrl-c to stop encoding
  
  Input stream #0:0 frame changed from rate:48000 fmt:s16p ch:2 chl:stereo to rate:48000 fmt:s16 ch:2 chl:stereo
  
  Detected 2 logical cores.
  
  [abuffer @ 0x2806e40] tb:1/48000 samplefmt:s16 samplerate: 48000 ch layout:0x3
  
  [abuffersink @ 0x2806fa0] auto-inserting filter 'auto-inserted fifo 0' between the filter 'audio format for output stream 0:0' and the filter 'output stream 0:0'
  
  No more output streams to write to, finishing.
  
  size=     900kB time=4.80 bitrate=1536.0kbits/s    
  
  video:0kB audio:0kB global headers:0kB muxing overhead 0.000000%

• Splitting webm video to png with transparency

  24 août 2016, par Stephen Emslie

  I need to split a webm encoded video into png frames, without losing transparency. I use the following ffmpeg command :

  ffmpeg -i dancer1.webm -pix_fmt rgba frames/%04d.png

  This produces a directory of pngs, but why is each output frame is missing transparency ?

  I have used this example video, which contains an alpha channel. See it playing over a background here. Here’s an example output frame from ffmpeg :

  

  ffmpeg produces the following output when it runs :

  ffmpeg version N-60294-g549f052 Copyright (c) 2000-2014 the FFmpeg developers                                             [1/2471]
  
    built on Feb  2 2014 05:41:56 with gcc 4.6 (Debian 4.6.3-1)
  
    configuration: --prefix=/root/ffmpeg-static/64bit --extra-cflags='-I/root/ffmpeg-static/64bit/include -static' --extra-ldflags='-L/root/ffmpeg-static/64bit/lib -static' --extra-libs='-lxml2 -lexpat -lfreetype' --enable-static --disable-shared --disable-ffserver --disable-doc --enable-bzlib --enable-zlib --enable-postproc --enable-runtime-cpudetect --enable-libx264 --enable-gpl --enable-libtheora --enable-libvorbis --enable-libmp3lame --enable-gray --enable-libass --enable-libfreetype --enable-libopenjpeg --enable-libspeex --enable-libvo-aacenc --enable-libvo-amrwbenc --enable-version3 --enable-libvpx
  
    libavutil      52. 63.100 / 52. 63.100
  
    libavcodec     55. 49.101 / 55. 49.101
  
    libavformat    55. 28.101 / 55. 28.101
  
    libavdevice    55.  7.100 / 55.  7.100
  
    libavfilter     4.  1.101 /  4.  1.101
  
    libswscale      2.  5.101 /  2.  5.101
  
    libswresample   0. 17.104 /  0. 17.104
  
    libpostproc    52.  3.100 / 52.  3.100
  
  Input #0, matroska,webm, from 'dancer1.webm':
  
    Metadata:
  
      encoder         : libwebm-0.2.1.0
  
    Duration: 00:01:02.83, start: 0.000000, bitrate: 520 kb/s
  
      Stream #0:0(eng): Video: vp8, yuv420p, 640x360, SAR 1:1 DAR 16:9, 30 tbr, 1k tbn, 1k tbc (default)
  
      Metadata:
  
        alpha_mode      : 1
  
  Output #0, image2, to 'frames/%04d.png':
  
    Metadata:
  
      encoder         : Lavf55.28.101
  
      Stream #0:0(eng): Video: png, rgba, 640x360 [SAR 1:1 DAR 16:9], q=2-31, 200 kb/s, 90k tbn, 30 tbc (default)
  
  Metadata:
  
    alpha_mode      : 1
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (vp8 -> png)

  Running identify on an output png produces this :

  $ identify 0001.png
  
  0001.png PNG 640x360 640x360+0+0 8-bit DirectClass 94.1KB 0.000u 0:00.000

  file has this to say about the png :

  $ file 0001.png
  
  0001.png: PNG image data, 640 x 360, 8-bit/color RGBA, non-interlaced

  Everything looks about right to me, so why don’t the output images contain an alpha channel ?