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• Combining a movie file with a text file

  12 décembre 2012, par Hugo

  Current Status : I have a movie I recorded on a microscopy and a .txt file with two columns : time and temperature. This file is synchronous with the video.
  I would like to 'edit' the video so there is a text box with the temperature that would update as the movie plays.

  My approach, for the moment, is to use ffmpeg. I managed to draw some text and it seems all is working as intended.

  The problem is : I can't find any reference on how to update that text dynamically. I am using some Python to read the file and launch ffmpeg with subprocess.

  I would like to ask if anyone knows some workaround for this. Maybe some other approach.

• iOS - Build/configure FFmpeg failing, "unable to create an executable file" ?

  9 juillet 2013, par golmschenk

  I'm attempting to build FFmpeg for iOS. I've tried following several tutorials on doing this (for example, tutorial 1, tutorial 2), all of which result in the same problem :

  /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/usr/bin/gcc is unable to create an executable file.
  
  C compiler test failed.

  The configuration setup I'm attempting to use is the following :

  ./configure \
  
  --prefix=armv7 \
  
  --disable-ffmpeg \
  
  --disable-ffplay \
  
  --disable-ffprobe \
  
  --disable-ffserver \
  
  --enable-avresample \
  
  --enable-cross-compile \
  
  --sysroot="/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS6.0.sdk" \
  
  --target-os=darwin \
  
  --cc="/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/usr/bin/gcc" \
  
  --extra-cflags="-arch armv7 -mfpu=neon -miphoneos-version-min=6.0" \
  
  --extra-ldflags="-arch armv7 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS6.0.sdk -miphoneos-version-min=6.0" \
  
  --arch=arm \
  
  --cpu=cortex-a9 \
  
  --enable-pic

  With this I have attempted replacing the compiler being used with virtually every compiler in /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/usr/bin. All of which still result in the same problem. Even just removing the --cc compiler parameter all together and using the default one on the system ends in the same problem. Any suggestion to how I might fix this ?

• Segmenting only specific parts of a video file

  30 mai 2013, par Christian P.

  I have some video files that I wish to serve up "dynamically", given the following workflow :

  1. Convert video from MP4 container to segmented .ts files with accompanying .m3u8 playlist
  2. Delete .ts files
  3. On request, generate .ts files (but only those requested, not for the entire video)

  I can generate .ts files for the entire video using ffmpeg using this command

  ffmpeg -y -i video.mp4 -c:a copy -bsf:a aac_adtstoasc -c:v copy -bsf:v h264_mp4toannexb -flags -global_header -map 0 -f segment -segment_time 10 -segment_list playlist.m3u8 -segment_format mpegts chunk_%03d.ts

  This is what I do in step 1 and it works just fine, video is playing fine. Due to disk constraints, I do not want to have two copies of every video (the original MP4 and the segmented .ts fies), so what I am trying to achieve is to find a command that will allow me to produce only the segments I need, on a per-request basis.

  Given the command above we may produce a sample playlist like this :

  #EXTM3U
  
  #EXT-X-VERSION:3
  
  #EXT-X-MEDIA-SEQUENCE:0
  
  #EXT-X-ALLOW-CACHE:YES
  
  #EXT-X-TARGETDURATION:12
  
  #EXTINF:11.261267,
  
  chunk_000.ts
  
  #EXTINF:11.261256,
  
  chunk_001.ts
  
  #EXTINF:7.507511,
  
  chunk_002.ts
  
  #EXTINF:11.261256,
  
  chunk_003.ts
  
  #EXTINF:11.261267,
  
  chunk_004.ts
  
  #EXTINF:7.507511,
  
  chunk_005.ts

  I have tried, using the -ss and -t flags available in ffmpeg, to create only a specific segments. For instance I might skip the first to segments by adding -ss 22.522523 (the total length of the two first segments), but this produces chunks that are not byte-for-byte identical to the original chunks and as such unusable (the video playback just stops). Is there a way to have ffmpeg (or another program) reproduce the same exact chunks, without producing all of them ?

  Short version : If I produce a playlist with chunks of an entire video (and accompanying .ts files), can I later reproduce a specific interval of those chunks that are byte-for-byte identical to the original chunks ?