Every 30th video packet has jitter

[fwolter]

I recorded the jitter of the incoming audio and video packets.

Audio has an average jitter of 30ms. This is consistent without any blips.

Video has an average jitter in the same range, but exactly every 30th video packet is arriving 260-300ms later than the others.

If we can eleminate the cause, we could reduce the buffer by 260ms leading to quicker channel switches.

I didn't check if the jitter comes from VDR or from this plugin, yet.

Here are the logs:

an 04 19:02:30 raspi vdr[61547]: [61570] [softhddevice][Sound] jittertracker: PacketReceived: video: high jitter detected: packet no.: 24: 285ms (last diff: 20ms, time diff: 305ms)
Jan 04 19:02:30 raspi vdr[61547]: [61570] [softhddevice][Sound] jittertracker: PacketReceived: video: high jitter detected: packet no.: 25: 214ms (last diff: 305ms, time diff: 91ms)
Jan 04 19:02:30 raspi vdr[61547]: [61570] [softhddevice][Sound] jittertracker: PacketReceived: video: high jitter detected: packet no.: 26: 91ms (last diff: 91ms, time diff: 0ms)
Jan 04 19:02:30 raspi vdr[61547]: [61570] [softhddevice][Sound] jittertracker: PacketReceived: video: high jitter detected: packet no.: 56: 282ms (last diff: 30ms, time diff: 312ms)
Jan 04 19:02:30 raspi vdr[61547]: [61570] [softhddevice][Sound] jittertracker: PacketReceived: video: high jitter detected: packet no.: 57: 221ms (last diff: 312ms, time diff: 91ms)
Jan 04 19:02:30 raspi vdr[61547]: [61570] [softhddevice][Sound] jittertracker: PacketReceived: video: high jitter detected: packet no.: 58: 91ms (last diff: 91ms, time diff: 0ms)
Jan 04 19:02:31 raspi vdr[61547]: [61570] [softhddevice][Sound] jittertracker: PacketReceived: video: high jitter detected: packet no.: 88: 266ms (last diff: 30ms, time diff: 296ms)
Jan 04 19:02:31 raspi vdr[61547]: [61570] [softhddevice][Sound] jittertracker: PacketReceived: video: high jitter detected: packet no.: 89: 214ms (last diff: 296ms, time diff: 82ms)
Jan 04 19:02:31 raspi vdr[61547]: [61570] [softhddevice][Sound] jittertracker: PacketReceived: video: high jitter detected: packet no.: 90: 72ms (last diff: 82ms, time diff: 10ms)
Jan 04 19:02:32 raspi vdr[61547]: [61570] [softhddevice][Sound] jittertracker: PacketReceived: video: high jitter detected: packet no.: 120: 247ms (last diff: 20ms, time diff: 267ms)
Jan 04 19:02:32 raspi vdr[61547]: [61570] [softhddevice][Sound] jittertracker: PacketReceived: video: high jitter detected: packet no.: 121: 193ms (last diff: 267ms, time diff: 74ms)
Jan 04 19:02:32 raspi vdr[61547]: [61570] [softhddevice][Sound] jittertracker: PacketReceived: video: high jitter detected: packet no.: 122: 74ms (last diff: 74ms, time diff: 0ms)
Jan 04 19:02:32 raspi vdr[61547]: [61570] [softhddevice][Sound] jittertracker: PacketReceived: video: high jitter detected: packet no.: 152: 270ms (last diff: 20ms, time diff: 290ms)
Jan 04 19:02:32 raspi vdr[61547]: [61570] [softhddevice][Sound] jittertracker: PacketReceived: video: high jitter detected: packet no.: 153: 216ms (last diff: 290ms, time diff: 74ms)
Jan 04 19:02:32 raspi vdr[61547]: [61570] [softhddevice][Sound] jittertracker: PacketReceived: video: high jitter detected: packet no.: 154: 74ms (last diff: 74ms, time diff: 0ms)
Jan 04 19:02:33 raspi vdr[61547]: [61570] [softhddevice][Sound] jittertracker: PacketReceived: video: high jitter detected: packet no.: 184: 259ms (last diff: 20ms, time diff: 279ms)
Jan 04 19:02:33 raspi vdr[61547]: [61570] [softhddevice][Sound] jittertracker: PacketReceived: video: high jitter detected: packet no.: 185: 197ms (last diff: 279ms, time diff: 82ms)
Jan 04 19:02:33 raspi vdr[61547]: [61570] [softhddevice][Sound] jittertracker: PacketReceived: video: high jitter detected: packet no.: 186: 82ms (last diff: 82ms, time diff: 0ms)
Jan 04 19:02:34 raspi vdr[61547]: [61570] [softhddevice][Sound] jittertracker: PacketReceived: video: high jitter detected: packet no.: 216: 260ms (last diff: 20ms, time diff: 280ms)
Jan 04 19:02:34 raspi vdr[61547]: [61570] [softhddevice][Sound] jittertracker: PacketReceived: video: high jitter detected: packet no.: 217: 198ms (last diff: 280ms, time diff: 82ms)
Jan 04 19:02:34 raspi vdr[61547]: [61570] [softhddevice][Sound] jittertracker: PacketReceived: video: high jitter detected: packet no.: 218: 72ms (last diff: 82ms, time diff: 10ms)
Jan 04 19:02:34 raspi vdr[61547]: [61570] [softhddevice][Sound] jittertracker: PacketReceived: video: high jitter detected: packet no.: 248: 247ms (last diff: 20ms, time diff: 267ms)
Jan 04 19:02:34 raspi vdr[61547]: [61570] [softhddevice][Sound] jittertracker: PacketReceived: video: high jitter detected: packet no.: 249: 196ms (last diff: 267ms, time diff: 71ms)
Jan 04 19:02:34 raspi vdr[61547]: [61570] [softhddevice][Sound] jittertracker: PacketReceived: video: high jitter detected: packet no.: 250: 71ms (last diff: 71ms, time diff: 0ms)
Jan 04 19:02:35 raspi vdr[61547]: [61570] [softhddevice][Sound] jittertracker: PacketReceived: video: high jitter detected: packet no.: 280: 236ms (last diff: 20ms, time diff: 256ms)
Jan 04 19:02:35 raspi vdr[61547]: [61570] [softhddevice][Sound] jittertracker: PacketReceived: video: high jitter detected: packet no.: 281: 185ms (last diff: 256ms, time diff: 71ms)
Jan 04 19:02:35 raspi vdr[61547]: [61570] [softhddevice][Sound] jittertracker: PacketReceived: video: high jitter detected: packet no.: 282: 71ms (last diff: 71ms, time diff: 0ms)
Jan 04 19:02:35 raspi vdr[61547]: [61570] [softhddevice][Sound] jittertracker: PacketReceived: video: high jitter detected: packet no.: 312: 261ms (last diff: 10ms, time diff: 271ms)
Jan 04 19:02:35 raspi vdr[61547]: [61570] [softhddevice][Sound] jittertracker: PacketReceived: video: high jitter detected: packet no.: 313: 209ms (last diff: 271ms, time diff: 62ms)
Jan 04 19:02:35 raspi vdr[61547]: [61570] [softhddevice][Sound] jittertracker: PacketReceived: video: high jitter detected: packet no.: 314: 62ms (last diff: 62ms, time diff: 0ms)
Jan 04 19:02:36 raspi vdr[61547]: [61570] [softhddevice][Sound] jittertracker: PacketReceived: video: high jitter detected: packet no.: 344: 239ms (last diff: 20ms, time diff: 259ms)
Jan 04 19:02:36 raspi vdr[61547]: [61570] [softhddevice][Sound] jittertracker: PacketReceived: video: high jitter detected: packet no.: 345: 188ms (last diff: 259ms, time diff: 71ms)
Jan 04 19:02:36 raspi vdr[61547]: [61570] [softhddevice][Sound] jittertracker: PacketReceived: video: high jitter detected: packet no.: 346: 71ms (last diff: 71ms, time diff: 0ms)
Jan 04 19:02:37 raspi vdr[61547]: [61570] [softhddevice][Sound] jittertracker: PacketReceived: video: high jitter detected: packet no.: 376: 260ms (last diff: 10ms, time diff: 270ms)
Jan 04 19:02:37 raspi vdr[61547]: [61570] [softhddevice][Sound] jittertracker: PacketReceived: video: high jitter detected: packet no.: 377: 186ms (last diff: 270ms, time diff: 84ms)
Jan 04 19:02:37 raspi vdr[61547]: [61570] [softhddevice][Sound] jittertracker: PacketReceived: video: high jitter detected: packet no.: 378: 84ms (last diff: 84ms, time diff: 0ms)
Jan 04 19:02:37 raspi vdr[61547]: [61570] [softhddevice][Sound] jittertracker: PacketReceived: video: high jitter detected: packet no.: 408: 254ms (last diff: 20ms, time diff: 274ms)
Jan 04 19:02:37 raspi vdr[61547]: [61570] [softhddevice][Sound] jittertracker: PacketReceived: video: high jitter detected: packet no.: 409: 203ms (last diff: 274ms, time diff: 71ms)
Jan 04 19:02:37 raspi vdr[61547]: [61570] [softhddevice][Sound] jittertracker: PacketReceived: video: high jitter detected: packet no.: 410: 71ms (last diff: 71ms, time diff: 0ms)

[rellla]

I recorded the jitter of the incoming audio and video packets.

Audio has an average jitter of 30ms. This is consistent without any blips.

Video has an average jitter in the same range, but exactly every 30th video packet is arriving 260-300ms later than the others.

To be correct, it's every 32th?

If we can eleminate the cause, we could reduce the buffer by 260ms leading to quicker channel switches.

I didn't check if the jitter comes from VDR or from this plugin, yet.

How should the jitter come from the plugin? You log that in every PlayVideo() and this is directly called by VDR. So if you can rule out, that there is no early return due to an invalid pes packet in between and the input buffer isn't full or at least VDR does a resend, when there was a "return 0", the plugin isn't involved!?
So imho this can only be caused by VDR or by the DVB stream itself.
I guess this would be an interesting question for vdr-portal. I would encourage you to open a thread ;)

[rellla]

Btw, did you test differents channels/transponders?

[fwolter]

The plugin could block the VDR main thread ocassionally leading to this late arrival, or there could be an error in the jitter measurement. Before raising an issue I want to do some further investigations.

EDIT: Another reason could be that the Fritzbox sends the packet too late or that the satip plugin delays the processing for some reason.

I tested two differend transponders.

I ran the jitter tracker over night and the max video jitter is 324ms. The max audio jitter was 34ms.

[rellla]

I will track the jitter, because i have a different input setup. DVB-S->Kathrein Exip 418->vtuner-ng

[rellla]

I just logged the overall jitter and have 422ms as a maximum (in a quick test period).
I have sth. in mind, that i read somewhere, where the 450ms come from - but can't remember. Iirc this depends on the stream provider?

[rellla]

Is this old thread related?

[fwolter]

Is this old thread related?

Not really sure...

If you comment in these lines, you can show whether you have the same behavior that every 30-32nd packet is late:
https://github.com/fwolter/vdr-plugin-softhddevice-drm-gles/blob/341c46c4cbfe61d52184d43de35f17b2fe6b334b/jittertracker.cpp#L61

[rellla]

This is what i get on DasErste HD via satip on rpi4:
https://pastebin.com/raw/HmmcCKad
There is a similar pattern, but not the same.
On ZDF for example i get logged stable maximums of ~100ms...
Imho we can't do much here?
Maybe we can introduce some learning algorithm, but i'm not sure, if it's worth the effort...

[rellla]

From my objections the jitter is depending on the stream. Not VDR and not the plugin itself. If you agree, I will close that one. too.
Maybe we should mention the observations somewhere in the developer doc...