live tv 'glitchy' until I pause and then play

[johnsonx42]

I'm not sure if this problem is new with 1.3.7, as I really never got things working enough with 1.2.13 to know if I had this problem.

For reference, I'm tuning OTA ATSC. I'm using the TS-Mux, and Cyberlink Video decoder (from PowerDVD 6). The Cyberlink decoder is using hardware acceleration, and shows CPU usage of about 35% while playing an HD source.

When I go into Live TV (Timeshifted, not Preview mode), the picture and sound glitch every second or two. At different times and on different channels, the effect varies from having smooth video with broken sound, to having the video and sound pause together. It also seems to happen only on HD channels; digital SD channels seem fine.

At first I just assumed I was getting a poor signal from my antenna, but then I realized that if I rewind back in the buffer it plays perfectly smooth.

A little more experimenting showed that all I have to do is press the 'Play' button on the remote (which seems to pause for the briefest moment and then resumes playing) and the glitching goes away. But, it returns as soon as I change channels.

I thought perhaps the 'Live TV Pre-Delay' might be the needed setting, but I increased this from the default 500ms to 1000ms, and then finally to 2000ms with no change at all in the effect.

Any suggestions?

Thanks.

[sub]

I dont know. Maybe try different decoders. Also make sure you have the audio renderer set to 'system default'.

[johnsonx42]

I will play around with the settings and decoders some more; the Cyberlink decoder is the only one I got a good picture with, but I suppose it would be useful to know if the same glitch occurs with the MPV or Nero 8 decoders (both of those had horrible problems with de-interlacing, and one of the two tended to dump back to the main menu after every channel change).

I was hoping this was something you or someone had seen, and had a check box or config file setting to fix.

[johnsonx42]

Ok, what is the 'Live TV Pre-Delay' setting supposed to do? In the wiki it says:

- the time to buffer LiveTV before being shown.

But if that's true, when I set it to the maximum of 4000ms (4 seconds), it should introduce a very obvious 4-second delay in changing channels (in addition to the time it takes for the tuning request, dumping the buffer, etc.). But I see absoltely no difference in time to change channels when I have the delay set to the default of 500ms vs 4000ms (edit: I also tried setting it zero, with no observable effect).

Is it possible this setting is broken, or am I completely misunderstanding what it is supposed to do?

[Pob]

I'm not sure if this problem is new with 1.3.7, as I really never got things working enough with 1.2.13 to know if I had this problem.

For reference, I'm tuning OTA ATSC. I'm using the TS-Mux, and Cyberlink Video decoder (from PowerDVD 6). The Cyberlink decoder is using hardware acceleration, and shows CPU usage of about 35% while playing an HD source.

When I go into Live TV (Timeshifted, not Preview mode), the picture and sound glitch every second or two. At different times and on different channels, the effect varies from having smooth video with broken sound, to having the video and sound pause together. It also seems to happen only on HD channels; digital SD channels seem fine.
SNIP
Thanks.

I think it's new in 1.3.7 - I posted about similar behaviour with the UK HD channels when using timeshift mode. It is as if PVRX2 is not getting the data fast enough, or unable to use the data fast enough. Like you, if I pause play even for a second, it will resume and play perfectly fine.
For me the biggest issue is when timeshift is not used and you try to watch the same HD channels - as I get a crash. Play starts the same as timeshift - jerky, stuttering, play, then PVRX2 keels over.
Is there any chance you could try live preview on your HD channels, to see what happens?

[johnsonx42]

The little bit I tested it, Live Preview seemed fine for me.

Oh, I should add that I've now had the problem occur on digital SD channels as well.

I think you and I are having the same problem with timeshift mode; I don't know if your problem with Live Preview is related or not.

It really seems as if the playback process is following the recording process a little too closely, continously hitting the bit of the stream that's currently being recorded. Thus pausing, even for the tinyest moment, backs the playback process off just enough to eliminate the problem.

This is why I'm looking at the 'Live TV Pre-Delay' setting, because it certainly sounds like it is supposed to deal with this issue. But as I posted above, as far as I can tell the setting does absolutely nothing.

[sub]

Does pressing Ctrl-D to skip back a bit help?

[johnsonx42]

yes, it does. Doing anything that backs the playback process off a bit resolves the skipping or glitching. Once I do that, the glitch will not return until I change channels.

Interestingly just pressing 'Play' (while it's already playing) makes the playback pause for just a tiny moment and then resume - that's enough to fix it.

[johnsonx42]

the plot thickens:

I've now confirmed that this effect occurs with every decoder I have: the Cyberlink PowerDVD 6 decoder, the Nero 8 decoder, and the MPV decoder.

What is even more interesting is that both the Nero 8 and MPV decoders tend to dump back to the main menu within a second or two (not always, but often, particularly after a channel change). This turns out to be part of the same problem: if I hit Play just as the video appears (ie, after selecting Live TV, or after a channel change), it prevents it from dumping back to the menu AND cures the 'glitching' effect at the same time.

It seems clear then that what is happening is that by default the LiveTV playback is playing too close to the end of the recording stream, so the playback stream glitches or skips. The Nero 8 and MPV decoders often die under this condition, while the Cyberlink decoder manages to cope with it. Pausing for just a moment to back the playback process off just a bit cures the problem.

I remain convinced (until someone explains otherwise) that this is exactly what the Live TV Pre-Delay setting is supposed to deal with, except that it's somehow broken in this release and perhaps in 1.2.13 as well. When I change the setting, it not only doesn't fix my problem, but it produces no observable effect whatsoever; I think I would notice a 4000ms delay vs a 0ms delay.

[sub]

Try the attached patch. It fixes the pre-play when using timeshift with TS.