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• mp3 decode error with ffmpeg in ios

  29 novembre 2016, par LL2012

  I met a very strange phenomenon in decoding mp3 to pcm data in ios pad.
  I have tested the code on windows 10, it works correctly.However, with the same mp3 file and the same code runing on ios pad , the pcm data become total white noise.

  I have compare the input compressed data(mp3) and the decoded data in memory on both system. input data is all the same(none silence frame),but the decoded data has totally different.

  so, can I say that there is a bug in ffmpeg on ios platforms for decoding audio.the version I used is ffmpeg2.6

  anyone meet the same things ?

• Recapping WebM’s First Week

  25 mai 2010, par noreply@blogger.com (John Luther) — webm, vp8, vorbis

  The WebM project launched last Wednesday with broad industry backing (watch video of the announcement). The list of supporters keeps growing with new additions such as the popular VLC media player, Miro Video Converter, HeyWatch cloud encoding platform, and videantis programmable processor platform. We’re also happy to see that future versions of IE will support playback of VP8 when the user has installed the codec.

  Our announcement sparked discussions in the community around the design and quality of our developer release. We’ve done extensive testing of VP8 and know that the codec can match or exceed the quality of other leading codecs. Starting this week, the engineers behind WebM will post frequently to this blog with details on how to make optimal use of its VP8 video codec and Vorbis audio codec. We are confident that the open development model will bring additional improvements that will further optimize WebM. In fact, the power of open development is already visible, with developers submitting patches and the folks at Flumotion enabling live streaming support in their product just three days after the project was launched.

  Keep an eye on this blog for regular updates on the adoption and development of WebM. To participate in the conversation or to ask questions of the WebM team, please join our discussion group.

  John Luther
  Product Manager, Google

  

• how to make any filter's value that accept integer value be a function of the timestamp in ffmpeg ? [closed]

  30 novembre 2023, par rosner altamira

  For example, i am trying to apply blur effect to video in ffmpeg using gblur filter, i want the blur strength to gradually increase from 0 to 50 in 2 secs starting at 5 secs and fade back from 50 to 0 in 3 secs thus finishing at 15 secs. In summary the blur is between 5 and 15 secs but from 5 to 7, the effect will gradually grow from 0 to 50 and from 12 to 15 it will fade from 50 back to 0.

  


  here is what i tried :

  


  


  ffmpeg -i test-video.mp4 -loop 1 -t 5 -i test-image.jpg -filter_complex "[0:v]gblur=sigma='if( lte(t,5) + gte(t, 15), 0, if( between(t, 7, 12), 50, min( max(25t - 125, 0), max(-16.67t + 250, 0) ) ) )':enable='between(t,5,15)'[bg] ;[1:v]fade=in:0:30[ol] ;[ol]fps=fps=15[ol] ;[bg][ol]overlay=(W-w)/2 :(H-h)/2:enable='between(t,5,15)'[out]" -map "[out]" -map 0:a output_video.mp4

  


  


  Expectations :

  


  


  [0:v]gblur=sigma='if( lte(t,5) + gte(t, 15), 0, if( between(t, 7, 12), 50, min( max(25t - 125, 0), max(-16.67t + 250, 0) ) ) )':enable='between(t,5,15)'[bg] :

  


  


  The blur strength depends dynamically on the time (t) as described above, controlled by the expression.
The enable parameter ensures that this filter is only applied between 5 and 15 seconds.

  


  


  [1:v]fade=in:0:30[ol] :
[ol]fps=fps=15[ol] :
[bg][ol]overlay=(W-w)/2 :(H-h)/2:enable='between(t,5,15)'[out] :

  


  


  The overlay input should be faded in for 2 secs starting from 5secs and will last 10secs (same time for the blur)

  


  As result, i am getting Invalid char error. Seems like sigma does not accept the "t" timestamp variable.