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• FFmpeg H264 encoder and Mediacodec AVC decoder bitstream format mismatch

  24 octobre 2023, par danvik13

  I have 2 apps : desktop and android part.
On desktop side I encode video using AVCodec H264 encoder and, then, send it to phone via net.
On the android side I receive a sequence of video packets and need to decode them from java code using MediaCodec AVC decoder

  


  The issue : according to Google docs, the decoder should be fed with two initial packets : csd-0 and csd-1, holding sps and pps accordingly. However, ffmpeg does not provide both of them. When I set AV_CODEC_FLAG_GLOBAL_HEADER, it forces the encoder to place initial data to the extradata field. But there is just one of the arrays

  


  Does AVC Mediadecoder guarantees that it will parse extradata bytes properly in case I will send them as a csd-0 buffer, ignoring csd-1 ?

  


  I know that extradata splitting can be done manually, but it is a bit weird that there is no clear way in ffmpeg to meet the bitstream format, required by Mediadecoder

  


  Explanation / solution / code snippets

  


• avcodec : h264 : Extract decoder methods

  31 juillet 2015, par David Holm

  avcodec : h264 : Extract decoder methods
  Extract two methods from decode_registered_user_data in order to improve
  
  code readability. Also make the constant holding the allocation size a
  
  64-bit unsigned integer so that the size comparison against INT_MAX makes
  
  sense.
  Bug-Id : CID1312090
  Signed-off-by : Luca Barbato <lu_zero@gentoo.org>
  

  • [DBH] libavcodec/h264_sei.c

• Add a text/caption to the first few seconds of a cut video ?

  6 mai 2022, par JR Jr.

  I want to cut a video and at the same time add a caption during the first few seconds of the video using drawtext. I have tried lots of different google searches but all turned out to be totally unhelpful for this specific purpose (even the answers on the SS pages). Also, I am on Windows, I don't care for other OS's, such as Unix/ubuntu/Mac.

  


  Let's use the below cut syntax as an example. It's cutting and changing the format from mkv to mp4, and I want to add a simple title to be displayed in the first 5 seconds of the video, since this will be done to various files and then they will be concatenated together and it's good to let the viewer know which movie each excerpt belongs to (without doing that manually for each single video, the goal is to add these texts to each of the below commands).

  


  "C:\ffmpeg\bin\ffmpeg.exe" -y -i "D:\S01\SATC - S01E03 - Bay of Married Pigs.mkv" -ss 00:18:05 -to 00:19:15 -codec copy "002-SATC - S01E03 - Bay of Married Pigs-00_18_05-00_19_15.mp4"


  


  Let's say I want to add the title "S01E03 - Bay of Married Pigs" in the center of the screen, in white, with font size 12, displayed between 1 and 5 seconds. How do I do that ?

  


  And more importantly, since these syntaxes tend to make the command line insanely long and it needs to be a one liner, is there a smarter way to feed the settings/configuration of the drawtext clause into the command line, as to not make the code very messy, long and chaotic ?
Besides, do white spaces matter/would misplaced blank spaces make the command line crash ?

  


  Been trying this for hours now, so I really appreciate your help on this.