Dash.js 4.7.4 freezes after seek

[hypn0z84]

Hi,

I have some issues with dash.js playback. I would like to understand what is the root cause of such behavior - player bug or some kind of problem with input data.

• Input data
  • Minute files was produced using ffmpeg each file processed separately.
  • Multi-period mpd file was built by joining mpd files of each minute with all needed modifications (passes conformance test).
  • Files attached.
• Problem
  • Playback in dash.js stalls once I seek near the end of each period eg. 00:47, 01:54, 02:50.
    • It happens only when destination location is not already in buffer - long jump.
    • If I wait long enough for player to fill the buffer with data of jump destination then this seek does not freeze the playback.
• I have tested this also in Shaka Player and haven't observed such behavior - tried hardly but I was not able to freeze it.

example.tar.gz

[dsilhavy]

This is unrelated to multiperiod. There is a time drift in your audio segments that accumulates over time. In the MPD you signal a segment duration of 1 second:

• duration / timescale = 1000000 / 1000000

Your audio segments are longer than one second, if you check the timestamps in the segments. For instance, audio segment 30 starts at:

EPT / timescale = 675840 / 22050 = 30,6503401361

After approximately 47 seconds, there is a drift by over one second. When you seek to 00:47 dash.js downloads a new segment based on the information in the MPD. Because of the drift, the segment we download for 00:47 starts at 00:48:04. Then there is a gap in the buffer which is larger than the duration of one segment (1 second) which is why the workaround after the seek does not kick in.

In summary, this is a content problem, but I check if we can be more robust and overcome this issue.

[hypn0z84]

Thank you Daniel for your response that was helpful.

It was my understanding that the FFmpeg would perform all the math magic for me especially when all the mpd examples that I saw use sample rate as a timescale for audio. I have played a bit with fractional values for audio segment duration. Tuned it to match sample rate / aac encoder frame size and now player works fine.
I have also checked the FFmpeg source code and in case of single_file it uses a hard-coded timescale=AV_TIME_BASE. It will use codec time base only when use_template and use_timeline options are provided.