[FFmpeg-trac] #2325(undetermined:open): MP4 AAC Audio is delayed by 2ms when converted to PCM

[FFmpeg]

#2325: MP4 AAC Audio is delayed by 2ms when converted to PCM
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             Reporter:  BChap        |                    Owner:  (none)
                 Type:  defect       |                   Status:  open
             Priority:  important    |                Component:
                                     |  undetermined
              Version:  git-master   |               Resolution:
             Keywords:  aac mov      |               Blocked By:
  regression                         |
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
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Comment (by Bartek Zdanowski):

 OK. I know all :)

 Some codes needs ramp-up samples. Some of them plenty, for example 2048 or
 more which can be more than one frame. It depends on the codec.
 Those samples are added in front of data that comes from the codec.
 One can check how many samples are added via
 VCodecContext::initial_padding;

 Those samples need to be discarded!
  This can be easily done if you're using ffmpeg as a library. But from
 command line this (to my best knowledge) cannot be discarded. If somebody
 knows a way - please add a comment.

 I've came up with a solution if initial_padding is different that a
 multiply of a frame size. You have to add missing samples to fill up to
 next full frame and discard those frames. Now you can push real audio data
 and enjoy output without latency and padding.


 This can be achieved only using ffmpeg as a library.
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/2325#comment:22>
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