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• Révision 115697 : Code inutile.

  16 juin 2019, par eric@smellup.net

  Appels avec le mauvais nombre d’arguments.
  updateq à la place de replace.

• Why does MP4 mdat atom not start with H.264 NALU start code ?

  1er mars 2019, par stevendesu

  I’m trying to investigate an issue with an MP4 that I’m generating returning the error :

  [mov,mp4,m4a,3gp,3g2,mj2 @ 0x55f0ae819080] Failed to add index entry
  
  Last message repeated 277 times
  
  [h264 @ 0x55f0ae81c300] Invalid NAL unit size (-800932280 > 6).

  The first frame decodes perfectly, and all future frames fail to decode. This results in a 0.042 second duration video.

  To help with the investigation, I had ffmpeg encode the same video in the same way so I could compare the two files. I noticed, however, that in the ffmpeg-encoded file the video sample doesn’t start with 0x000001 or 0x00000001.

  I tried looking through the MP4 spec and the H.264 spec to understand why this start code is sometimes required but not required in this case, but there literally hundreds of pages and I couldn’t find anything in a day of reading.

  The ffmpeg-generated file is available here : http://files.stevendesu.com/test.mp4

  If you open this with an MP4 atom parser you’ll notice the first mdat atom starts :

  0000 6DF4 6D64 6174 0000 04BF 6588 8101
  
  1788 8C12 0001 1498 3800 188E 003F FFFC
  
  ...

  The first 8 bytes make sense : 00006DF4 (28148) = the size of the mdat atom, 6D646174 = "mdat" in ASCII

  After this the mdat atom starts with 0x000004. According to the traf atom in the preceding moof, the first video sample (with a duration of 800/16000 seconds and a size of 19899 bytes) should start exactly here. Therefore 0x000004 are the first 3 bytes of the first video sample.

  Either this video sample doesn’t start with a NALU start code, or there is some header / wrapper around the NALU that I don’t understand.

  Can anyone explain to me why this video sample doesn’t start with a NALU start code ?

• PHP ffmpeg having problem extracting Image as a thumbnail

  19 décembre 2022, par Sarotobi

  I am using a below repo via composer everything works well but i have a problem extracting the image as a poster ( thumbnail )

  


  https://github.com/aminyazdanpanah/PHP-FFmpeg-video-streaming#extracting-image

  


  I used below code.

  


  $video = $ffmpeg->open('./videos/example1.mp4");
$frame = $video->frame(FFMpeg\Coordinate\TimeCode::fromSeconds(51));
$frame->save('/var/media/poster.jpg');


  


  But got an error below using mac os

  


  Fatal error: Uncaught Alchemy\BinaryDriver\Exception\ExecutionFailureException: ffmpeg failed to execute command '/usr/local/bin/ffmpeg' '-y' '-ss' '00:00:51.00' '-i' './videos/example1.mp4' '-vframes' '1' '-f' 'image2' './videos/example1/poster.jpg': Error Output: ffmpeg version N-109428-g10a56363a7-tessus https://evermeet.cx/ffmpeg/

  


  Just want to know what is missing, i have already run chmod -R 0777 . to have a sufficient permissions.