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• mp4 And Rotation - Remove Flags But Set Rotation

  7 avril 2024, par Bud

  I'm having a hard time with the rotation on some mp4 files I have. It may well be my poor understanding, so forgive me if I set out what I know (or think I know) and then what I want to happen.

  


  An mp4 has, obviously, a right way up - that is, the way you want it to show when you watch it. Call this the orientation. This isn't metadata - it's just the way you, as a person, want to see the image, with people's heads at the top of the screen and their feet at the bottom.

  


  As part of the metadata, mp4 files have a value/parameter (I believe called 'rotate') that tells how much the mp4 needs to be rotated (0, 90, 180, 270 degrees) so that it is correctly oriented. This value/parameter is observed by some players and not by some others. So if I play my video using this player, all is good (because it observes the value/parameter) - but if I play it with that other player, everything is sideways (because it doesn't observe the value/parameter).

  


  What I want to do is orient the mp4 correctly with the value/parameter set to 0, so that no matter what player plays it, it will always be played oriented correctly (because those players that observe the value/parameter will see it's 0 and do nothing). So I think what I need to do is somehow remove the value/parameter, then rotate the mp4 to the correct orientation without using the rotate value/parameter. I'm thinking of something like what FastStone Image Viewer can do with JPGs - rotate them losslessly without setting the rotate value.

  


  I've used ffmpeg and believe that it removed the rotate value/parameter (or set it to 0) because after I used it, suddenly my video appeared sideways in Windows Explorer, where previously it had appeared right way up. But how do I now rotate it to the correct orientation without changing the rotate value/parameter ?

  


  Sorry, this is very long winded and confused. Just like me.

  


• Random PIPELINE_ERROR_DECODE : video decoder reinitialization failed on Chromium HTML5 video tag

  9 janvier 2024, par Hello World

  System

  


  Running an Expo React Native app, with a <webview></webview> component that loads a NextJS app with an HTML5 <video></video> tag. The system with issues is running the app on Android 9.0 with WebView implementation set to Android System WebView 84.0. The system without issues is running the app on Android 10.0 with WebView implementation set to Android System WebView 120.0.

  


  Details

  


  Video files being played by the <video></video> element are previously transcoded by the following fluent-ffmpeg node package :

  


  import ffmpeg from 'fluent-ffmpeg'

ffmpeg(rawVideoFileUrl)
  .videoCodec('libx264')
  .audioCodec('aac')
  .outputOption('-strict experimental')
  .outputOption('-movflags frag_keyframe+faststart')
  .format('mp4')


  


  My knowledge on video transcoding is very limited, but I have to do the transcoding to guarantee that the files are compatible to be played by my NextJS web app. In my research, my findings pointed to these FFMPEG command line arguments for my purpose.

  


  For the aforementioned WebView version, H.264 with AAC, should be compatible, yet playback is not stable. Many times it will play just fine, but other times I receive the error :

  


  PIPELINE_ERROR_DECODE: video decoder reinitialization failed


  


  If I refresh the web app, it works again. That leads me to believe it is somehow memory related, maybe caused by incompatibility.

  


  I'm not sure whether video decoder reinitialization failed produced by the HTML5 <video></video> tag is a problem of transcoding or not, as the videos play fine most of the time and only produces that error in the console some of the times, unexpectedly.

  


  Question

  


  Is there something that I can do to the fluent-ffmpeg command to make the video files more widely compatible, including the WebView 84.0 system too, or is the issue somewhere else ?

  


  In this case, updating WebView is not an option.

  


• avcodec/arm/sbcenc : avoid callee preserved vfp registers

  25 août 2019, par James Cowgill

  avcodec/arm/sbcenc : avoid callee preserved vfp registers
  When compiling FFmpeg with GCC-9, some very random segfaults were
  
  observed in code which had previously called down into the SBC encoder
  
  NEON assembly routines. This was caused by these functions clobbering
  
  some of the vfp callee saved registers (d8 - d15 aka q4 - q7). GCC was
  
  using these registers to save local variables, but after these
  
  functions returned, they would contain garbage.
  Fix by reallocating the registers in the two affected functions in
  
  the following way :
  
   ff_sbc_analyze_4_neon : q2-q5 => q8-q11, then q1-q4 => q8-q11
  
   ff_sbc_analyze_8_neon : q2-q9 => q8-q15
  The reason for using these replacements is to keep closely related
  
  sets of registers consecutively numbered which hopefully makes the
  
  code more easy to follow. Since this commit only reallocates
  
  registers, it should have no performance impact.
  Signed-off-by : James Cowgill <jcowgill@debian.org>
  
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DH] libavcodec/arm/sbcdsp_neon.S