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• Wrap a stream of raw H264 NALUs into a container like MP4

  7 mai 2012, par cloudraven

  I have an application that sends raw h264 NALUs as generated from encoding on the fly using x264 x264_encoder_encode. I am getting them through plain TCP so I am not missing any frames.
  I need to be able to decode such a stream in the client using Hardware Acceleration in Windows (DXVA2). I have been struggling to find a way to get this to work using FFMPEG. Perhaps it may be easier to try Media Foundation or DirectShow, but they won't take raw H264.
  I either need to :

  1. Change the code from the server application to give back an mp4 stream. I am not that experienced with x264. I was able to get raw H264 by calling x264_encoder_encode, by following the answer to this question : How does one encode a series of images into H264 using the x264 C API ? How can I go from this to something that is wrapped in MP4 while still being able to stream it in realtime

  2. I could at the receiver wrap it with mp4 headers and feed it into something that can play it using DXVA. I wouldn't know how to do this

  3. I could find another way to accelerate it using DXVA with FFMPEG or something else that takes it in raw format.

  An important restriction is that I need to be able to pre-process each decoded frame before displaying it. Any solution that does decoding and displaying in a single step would not work for me

  I would be fine with either solution

• ffmpeg quality issues

  4 mai 2012, par Chris Vincze

  I'm trying to encode MPEG2 files for broadcast. The spec is MPEG-2 @ 50Mbps with all frames as intra frames.

  So I've done a few experiments and have come across a conundrum.

  Setting the q flags like this :

  ffmpeg -i input.%04d.dpx -vcodec mpeg2video -pix_fmt yuv422p -intra -qmin 1 -qscale 1 -output.mpg

  gives a constant q=1.0 while transcoding and produces a file of approximately 25Mbps (although weirdly the file bitrate is given as : bitrate : 25551 kb/s while the actual stream is specified as 104857 kb/s)

  Duration : 00:01:29.95, start : 1.000000, bitrate : 25551 kb/s
  Stream #0.0[0x1e0] : Video : mpeg2video, yuv422p, 720x608 [PAR 608:405 DAR 16:9], 104857 kb/s, 25 fps, 25 tbr, 90k tbn, 50 tbc
  Stream #0.1[0x1c0] : Audio : mp2, 48000 Hz, 2 channels, s16, 384 kb/s

  However, specifying a constant bit rate like this :

  ffmpeg -i input.%04d.dpx -vcodec mpeg2video -pix_fmt yuv422p -intra -b 50000k -minrate 50000k -maxrate 50000k -bufsize 2000000 -output.mpg

  gives a varying q whilst transcoding somewhere between 1 and 6. The resulting file is 50Mbps (in both the file and the video stream)

  However the quality of this file is not as good as the 25Mbps (as suggested by the q factor).

  So my question is how can I produce a file of 50Mbps AND q=1. It is my understanding that the q flags and the bitrate flags are mutually exclusive (I've tried running both).

  Thanks very much for your help.

• Transcoding Mp4 video on Android with FFMPEG

  18 octobre 2012, par geeknizer

  I've compiled FFMPEG binary from Bambuser project (refer question) and have pushed binary and .so files to application directory.

  But when I try running FFMPEG with input file, it always complains file not found.

  1|root@android:/data/data/com.bambuser.broadcaster # ls                        
  
  cache           libavcodec.so   libavfilter.so  libswscale.so
  
  ffmpeg          libavcore.so    libavformat.so  tutorial.mp4
  
  lib             libavdevice.so  libavutil.so
  
  1|root@android:/data/data/com.bambuser.broadcaster # ./ffmpeg -i tutorial.mp4 out.mp4                                                              
  
  FFmpeg version UNKNOWN, Copyright (c) 2000-2010 the FFmpeg developers
  
    built on May  8 2012 10:11:37 with gcc 4.4.3
  
    configuration: --target-os=linux --cross-prefix=arm-linux-androideabi- --arch=arm --sysroot=/home/tarandeep/tools/android-ndk/platforms/android-3/arch-arm --soname-prefix=/data/data/com.bambuser.broadcaster/lib/ --enable-shared --disable-symver --enable-small --optimization-flags=-O2 --disable-everything --enable-encoder=mpeg2video --enable-encoder=nellymoser --prefix=../build/ffmpeg/armeabi-v7a --extra-cflags='-march=armv7-a -mfloat-abi=softfp' --extra-ldflags=
  
    libavutil     50.34. 0 / 50.34. 0
  
    libavcore      0.16. 0 /  0.16. 0
  
    libavcodec    52.99. 1 / 52.99. 1
  
    libavformat   52.88. 0 / 52.88. 0
  
    libavdevice   52. 2. 2 / 52. 2. 2
  
    libavfilter    1.69. 0 /  1.69. 0
  
    libswscale     0.12. 0 /  0.12. 0
  
  tutorial.mp4: No such file or directory

  I've tried placing file in /sdcard and other locations, I always get same output