Chapter Marks lead to wrong playback position

Bug report
1

App version: 3.6.1 Google Play
Android version: 14
Device model: moto g34 5G

Expected behaviour: When selecting a chapter mark the playback position should be placed at the correct position.

Current behaviour: Selecting a chapter mark leads to a position slightly off its intended position. The offset seems to be larger the later in the show the timecode is.

First occurred: n/a

Steps to reproduce:

  1. Download a podcast with chapter marks.
  2. Play the episode and choose any chapter mark
  3. Compare the playback position with other apps or spotify etc. AntennaPod is off by several seconds sometimes, unfortunately.

edit: Please compare the actual playback position, not the timecode displayed.

I also discovered that although a show is still playing near the end AntennaPod already shows 0:00:00 time remaining. Yet it still plays the show until it is really finished.

Tested with my own Podcast 16bit, 48kHz, 128kbit/s CBR, Mono

1 Like
2

I don’t use chapter marks, but recently I noticed the same issue with the counter indicating you’re at the end while the file continues to play to the end.

3

Same behaviour on Google Pixel 8. It seems to me that the timer on the progress bar is inaccurate. So for example, the mp3 metadata says 30’‘07", and if one goes to the chapter start, the timer shows 30’07". BUT, the audio playing is actually from 30’'02"

4

The reason why this happens is that some podcast hosting companies dynamically add advertisements to media files (cutting them on-the-fly) without shifting the chapter marks accordingly. Unfortunately this is outside the control of AntennaPod

5

I’ve definitely seen that kind of thing, like when the downloaded episode is longer than the listed length before I downloaded it.

6

Hi ByteHamster and all, Thank you for the response. Yes I understand your point and it chimes with my experience. I should have put more detail in my post. In my test, the mp3 file did not go through a podcast publishing process.
I took a mp3 file that I made - total duration 47’50".704
FFprobe.exe shows the chapter metadata as:
“…
Chapters:
Chapter #0:0: start 1807.543000, end 2870.704000
Metadata:
title : Part 2
Stream #0:0: Audio: mp3 (mp3float), 48000 Hz, stereo, fltp, 320 kb/s
…”
1807.543 seconds works out as 30’7".543

That time value when played in VLC on a computer, correctly positions the marker at a small period of silence in the audio, where I positioned the chapter marker.

When that same MP3 file is added to AntennaPod, the chapter marker shows the time as 30’07", but that is not from where the audio starts playing.
Thanks
Richard

7

Hi Richard_Courtice,

I had a similar problem. I found a solution.

I discovered that the problem was related to “start” tag.

On the podcast file, ffprobe -i podcast.mp3 displayed

Duration: 01:29:56.53, start: 0.025057, bitrate: 128 kb/s

I used the “-write_xing 0” option of ffmpeg to set start to 0 :

ffmpeg -i podcast.mp3 -write_xing 0 -acodec copy output.mp3

And then, with output.mp3 file the chapters marks lead to right playback position.

Hopes it is useful for you.