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• libavfilter - reconfigure filter graph using avfilter_graph_parse_ptr returns -22

  16 juillet 2021, par Rahul

  I am using transcode.c sample from ffmpeg examples and it is working as expected. It uses avfilter_graph_parse_ptr to setup filter graph and it works fine.

  


  However, I need change filter graph dynamically and there avfilter_graph_parse_ptr fails. It returns -22. I am not certain if it is a valid operation to do (reconfigure) ? If it is possible, does it require more than avfilter_graph_parse_ptr and avfilter_graph_parse_ptr ? libavfilter documentation doesn't say anything about reconfigure or reset existing graph.

  


  I can create a new graph but I am avoiding it since it is affecting the existing buffers.

  


  Thank you for your insight.

  


• pass ffmpeg options through mlt xml

  17 avril 2021, par carsten

  I'm looking at an MLT XML file that I created with kdenlive and would like to tweak the command line options passed to ffmpeg.

  


  If I understand correclty, this is the part that I need to edit :

  


   <consumer f="mp4" g="15" channels="2" crf="15" progressive="1" target="thetargetfile.mp3" threads="0" vcodec="libx264" ab="256k" movflags="&#x2B;faststart" bf="2" preset="faster" acodec="aac" in="0" out="18263"></consumer>&#xA;

  


  Now, I would like to pass an additional flag to ffmpeg, in my case -stillimage for still image optimization of the output (my file is a recorded slideshow presentation, so there's really no excuse for it being hundreds of MB large).

  


  Is there an option in that allows to just pass arbitrary flags to ffmpeg, or how else would I go about performing such an optimization ?

  


• How to use ffmpeg / x264 2-Pass encoding for multiple bitrate output files

  10 septembre 2019, par Jonesy

  While performing a 2-Pass encode to multiple output files I was receiving the error

  



  ratecontrol_init: can't open stats file 1 ffmpeg2pass-2.log


  



  My setup is to do a single first pass and then multiple second pass encodes to output files with different target bitrates using the same first pass results.

  



  ffmpeg -y -i $INPUT_FILE -an -vcodec libx264 -pass 1 -b:v 700k -f rawvideo /dev/null

ffmpeg -y -i $INPUT_FILE -i out-aud.mp4 \
$AUDIO_OPTIONS_P2 -vcodec libx264 -pass 2 -b:v 250k -f mp4 out-250.mp4 \
$AUDIO_OPTIONS_P2 -vcodec libx264 -pass 2 -b:v 500k -f mp4 out-500.mp4 \
$AUDIO_OPTIONS_P2 -vcodec libx264 -pass 2 -b:v 700k -f mp4 out-700.mp4


  



  This sequence resulted in the error listed above. What I discovered thru code-inspection is that ffmpeg/x264 looks for a different set of first-pass files for each second-pass encoding path. The first encoding path uses the set of files originally created

  



  ffmpeg2pass-0.log
ffmpeg2pass-0.log.mbtree


  



  The second encoding path requires first-pass files with the names

  



  ffmpeg2pass-2.log
ffmpeg2pass-2.log.mbtree


  



  The third encoding path requires first-pass files with the names starting with ffmpeg2pass-4*, etc.

  



  My solution was to create soft-links to the originally created set of files with the new names that were required for each pass before running the second-pass command.

  



  ln -s ffmpeg2pass-0.log ffmpeg2pass-2.log
ln -s ffmpeg2pass-0.log.mbtree ffmpeg2pass-2.log.mbtree
ln -s ffmpeg2pass-0.log ffmpeg2pass-4.log
ln -s ffmpeg2pass-0.log.mbtree ffmpeg2pass-4.log.mbtree


  



  This seems to work as it results in the output encodes that I needed. However, I don't know if this method is legitimate. Am I getting sub-optimal encoding results by using a first-pass output for one bitrate (700k) as the input to second-pass encodings for other bitrates ?