Recherche avancée

Sur d’autres sites (7069)

• C++/CLI FFmpeg av_read_frame returns a size but no data ?

  26 novembre 2013, par tommed

  I have written some C code to access ffmpeg and wrapped it in a C++/CLI (.NET managed) class. The program fetches a live video stream and extracts frames and converts them to PNG files.

  Unfortunately the images that are saved to disk are always black (opening them in Notepad++ shows that they are full of nulls).

  I am using the assemblies aformat/codec-55.dll and the development headers and libs for compilation from ffmpeg-20131120-git-e502783-win64-dev. The whole project is compiled using Managed C++ (Cpp/cli) .NET 4.0 for 64-bit.

  After some investigation the problem appears to be that av_read_frame fills the AVPacket->size value correctly, but the AVPAcket->data is always null. When the frame is finished (got==1) then the data for the AVFrame is just a matrix of nulls. :(

  Here is the code :
  Example code (sorry, but it didnt paste well into SO)

  I think the problem is at line 34 when the packet is returned like so :
  

  Please, how can I get this to work ? What have I done wrong ?

• ffmpeg conversion to mpeg2video

  19 novembre 2013, par spicyramen

  Need to play some video files from a Cisco DMP, and need to use mpeg2video for video and mp2 for audio.

  Im using ffmpeg -i to verify video format.

  This video plays correctly :

  Input #0, mpeg, from 'ATT_Telepresence_Scheduling.mpg':
  
    Duration: 00:07:14.08, start: 0.522456, bitrate: 474 kb/s
  
      Stream #0:0[0x1e0]: Video: mpeg2video (Main), yuv420p, 600x340 [SAR 1:1 DAR 30:17], 29.97 fps, 29.97 tbr, 90k tbn, 59.94 tbc
  
      Stream #0:1[0x1c0]: Audio: mp2, 44100 Hz, stereo, s16p, 128 kb/s

  This video does not play(Black screen) :

  Input #0, mpegts, from 'Telepresence_part2.ts':
  
  Duration: 00:02:32.83, start: 1.000000, bitrate: 8783 kb/s
  
  Program 1 
  
  Stream #0:0[0x45]: Audio: aac ([15][0][0][0] / 0x000F), 48000 Hz, stereo, fltp, 163 kb/s
  
  Stream #0:1[0x44]: Video: h264 (Main) ([27][0][0][0] / 0x001B), yuv420p, 1280x720 [SAR 1:1 DAR 16:9], 29.92 fps, 29.92 tbr, 90k tbn, 59.82 tbc

  How to perform the conversion to mpeg and to video mpeg2video and audio mp2 and preserve HD quality ?

• Add an image as watermark to a video file with ffmpeg [migrated]

  19 novembre 2013, par Alex Flo

  I would like to add a text to a video file with FFMPEG. While I was able to do this with plain text

  $FFMPEG -y -i $SOURCE \
  -vf drawtext="fontfile=/usr/share/fonts/Lato-Reg-webfont.ttf:fontsize=40:box=1:boxcolor=black:fontcolor=white:text='$WATERMARK':x=(main_w-text_w)-10:y=(main_h-text_h)-4" \
  -threads $THREADS -f mp4 -vcodec mpeg4 -b $MOBILE_BITRATE -r $MOBILE_FRAME_RATE -strict -2 \
  -s $RESOLUTION_SD -acodec libfaac -ar $MOBILE_AUDIO_RATE -ac $MOBILE_AUDIO_CHANNELS -ab $MOBILE_AUDIO_BITRATE \
  $VIDEONAME_MOBILE-android.mp4

  this won't look good enough. So I tried with adding a transparent PNG file as a watermark. Looking for examples I tried like this :

  $FFMPEG -y -i $SOURCE \
  -vf "movie=$WATERMARK_SMALL_PATH [watermark] ; [in][watermark] overlay=10:main_h/2-overlay_h/2 [out]" \
  -threads $THREADS -f mp4 -vcodec mpeg4 -b $MOBILE_BITRATE -r $MOBILE_FRAME_RATE -strict -2 \
  -s $RESOLUTION_SD -acodec libfaac -ar $MOBILE_AUDIO_RATE -ac $MOBILE_AUDIO_CHANNELS -ab $MOBILE_AUDIO_BITRATE \
  $VIDEONAME_MOBILE-android.mp4

  it won't work. I can share the exact error output if that could be useful to anyone.