Recherche avancée

Sur d’autres sites (8437)

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

  2 décembre 2014, 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 ?

• FFMpeg : Take Certain Amount of Screenshots Between X and X ?

  4 mai 2014, par user1445975

  Is there any way to get ffmpeg to take X number of screenshots between X time and X time ? The way I’m doing my command line code now is like this :

  ffmpeg -ss 79 -i 1.avi -r 1/2.15 -f image2 1_%%05d.jpg

  This method only starts taking screenshots starting at 79 seconds, but I can’t figure out a way to set an ending time (before the video ends).

  Also, I will be displaying these video screenshots on a website and want there to be the same amount of screenshots per video file for consistency purposes. Is there a way to set how many screenshots I want from a video ? As in, ffmpeg figures out how much time is between the two points I specify, then figures out how often to take a screenshot based on how many I want total from a video ?

• Does a packet taken from FFMPEG have absolue time information ?

  12 août 2012, par prosopher

  I'm creating a video player which works with an incomplete video file in which it has some empty(incomplete) sections filled with zeros.

  For example, there's a video file which has section A, B, and C in sequence. A and C are complete and B is incomplete. And A section starts from file offset 0 and includes header information as well.

  Now, I want to know a starting time of section C.

  So I read packets from section A to section C entirely by using FFMPEG and it skipped section B which was what I wanted. But when I took presentation timestamp values from each packet while reading, I found it continuously increasing.

  The problem is I want timestamps from section C to be increased by the amount of section B.

  Even though section B is ignored, I want to know the actual time when I'm supposed to present section C.

  I guess FFMPEG doesn't include absolute time information but calculates time to present a packet based on the last packet's time information which is relative. However, I assume there must be a way to find the absolute time information.