Hi There,
I am trying to MUX H264 video and AAC audio into a TS file. The sources of
these streams are separate and provide NTP timestamps for each frame.
I have decided to go with video master TS mode to use NTP timestamp of first
video frame as reference to calculate PTS values before MUXing. I also drop all
the audio frames received before first video frame.
I am not able to achieve proper AV sync and my audio is leading by the
difference in NTP timestamps of respective first frames.
e.g.
1. First Video Frame - NTP 11:00:00:000 - Duration 30mSec
- PTS=0 timebase{1,90000}
2. First Audio Frame - NTP 11:00:00:040 - Duration 70 mSec - PTS=
3600 timebase{1,90000}
3. Second V Frame - NTP 11:00:00:030 - Duration 30mSec
- PTS= 2700 timebase{1,90000}
4. Third V Frame - NTP 11:00:00:060 - Duration 30mSec
- PTS= 7200 timebase{1,90000}
5. Forth V Frame - NTP 11:00:00:090 - Duration 30mSec
- PTS= 8100 timebase{1,90000}
6. Second A Fram - NTP 11:00:00:110 - Duration 70mSec
- PTS= 9900 timebase{1,90000}
7. Fifth V Frame - NTP 11:00:00:120 - Duration 30mSec
- PTS= 10800 timebase{1,90000}
For the above case the drift is 40mSec. If I correct Audio sync by -40mSec VLC
plays the video just fine.
Please let me know if my logic is right and if not suggest a correction. Am I
supposed to set an output_ts_offset to correct the drift and if yes how to do
that?
Regards,
Ameya Tambekar
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