[FFmpeg-devel] mpegaudio_parser question

Karsten Otto ottoka at posteo.de
Sun Jun 17 17:56:53 EEST 2018

Hi list,

I have a question about mpegaudio_parser. I see that it keeps any packet data before a frame header, instead of discarding it. This makes sense, because it usually can combine this data with the leftovers from a previous packet to complete a frame. But the parser also does this when just starting up, i.e. after a seek. I had expected it to discard the preceding data in this case. So, is this expected behaviour? Am I using it wrong?

Background: I am trying to add seek capability to libavformat/aadec. Unfortunately, when the format contains MP3 content, its frames do *not* align with the internal crypto chunk boundaries. So when seeking to a valid chunk start, it usually lands in the middle of an MP3 frame. Given the behaviour of the mpegaudio_parser, there is always some audible glitch. I can work around this by adding my own MP3 header detection, but that would not be very DRY. So, what is the proper way of handling this case? Any suggestions?


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