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0.25 Major AV sync problems

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dmoo1790 at ihug

Jun 3, 2012, 2:25 AM

Post #1 of 33 (1717 views)
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0.25 Major AV sync problems

Audio/Video sync has not been good for me ever since I upgraded to 0.25.
But since I haven't seen others complaining I wonder if I have a config
problem. Here's what I see:

- OSD of Playback Data frequently shows A/V Sync values of around -2 and
never "pulls in" to lower values without user intervention.
- Actual AV sync is not as bad as -2 seconds but is a large fraction of
a second.
- Seeking forwards or backwards almost always degrades AV sync.
- Pausing/unpausing usually, but not always, helps AV sync.
- Seeking back to the start of a recording loses sync for a few seconds
and sometimes never recovers. Audio and/or video may break up.
Ridiculously huge AV sync values are shown in the OSD and frontend log.
- After seeking to the start and breaking sync it seems seeking forward
recovers sync.

So am I the only one seeing this? If so, what is the magic config option
that I'm missing?
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support at drdos

Jun 3, 2012, 3:22 AM

Post #2 of 33 (1683 views)
Permalink

Re: 0.25 Major AV sync problems [In reply to]

David Moore wrote:
> So am I the only one seeing this? If so, what is the magic config
> option that I'm missing?

I'm in the US and don't see this. I'm using a PVR-500 and an HDHR.

Doug

--
Ben Franklin quote:

"Those who would give up Essential Liberty to purchase a little Temporary Safety, deserve neither Liberty nor Safety."

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peper03 at yahoo

Jun 7, 2012, 3:11 PM

Post #3 of 33 (1625 views)
Permalink

Re: 0.25 Major AV sync problems [In reply to]

On 03/06/12 11:25, David Moore wrote:
> Audio/Video sync has not been good for me ever since I upgraded to
> 0.25. But since I haven't seen others complaining I wonder if I have a
> config problem. Here's what I see:
>
> - OSD of Playback Data frequently shows A/V Sync values of around -2
> and never "pulls in" to lower values without user intervention.
> - Actual AV sync is not as bad as -2 seconds but is a large fraction
> of a second.
> - Seeking forwards or backwards almost always degrades AV sync.
> - Pausing/unpausing usually, but not always, helps AV sync.
> - Seeking back to the start of a recording loses sync for a few
> seconds and sometimes never recovers. Audio and/or video may break up.
> Ridiculously huge AV sync values are shown in the OSD and frontend log.
> - After seeking to the start and breaking sync it seems seeking
> forward recovers sync.
>
> So am I the only one seeing this? If so, what is the magic config
> option that I'm missing?

I'm getting this too. Playback data shows A/V sync generally at around
+/-2. Pausing/unpausing usually seems to fix it (A/V sync goes to
something like 0.17). Skipping makes it worse.

I haven't been able to do too much playing around with it but it seems
that even after pausing/unpausing, after a while I notice it's got out
of sync a bit. When I could check, I think A/V sync was showing around 1.x.

I thought it might only be on HD/AC3 content but I think it happens on
SD/MP2 stuff too. All my recordings come in via DVB-S(2).

At least the pause/unpause trick generally seems to work but it doesn't
help the WAF when I have to do it several times during a recording (she
doesn't seem to notice but it drives me up the wall!).

Richard.
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mythtv-users at needhammarket

Jun 7, 2012, 3:23 PM

Post #4 of 33 (1631 views)
Permalink

Re: 0.25 Major AV sync problems [In reply to]

I'm getting this issue in the UK, with SD recordings from DVB-T
sources. As you say, it seems to be more noticeable with 0.25 than it
was with 0.24 - and seems to increase when skipping ads. I haven't
tried the pause/unpause trick, but it drives me up the wall too!

On 7 June 2012 23:11, Richard <peper03 [at] yahoo> wrote:
> On 03/06/12 11:25, David Moore wrote:
>>
>> Audio/Video sync has not been good for me ever since I upgraded to 0.25.
>> But since I haven't seen others complaining I wonder if I have a config
>> problem. Here's what I see:
>>
>> - OSD of Playback Data frequently shows A/V Sync values of around -2 and
>> never "pulls in" to lower values without user intervention.
>> - Actual AV sync is not as bad as -2 seconds but is a large fraction of a
>> second.
>> - Seeking forwards or backwards almost always degrades AV sync.
>> - Pausing/unpausing usually, but not always, helps AV sync.
>> - Seeking back to the start of a recording loses sync for a few seconds
>> and sometimes never recovers. Audio and/or video may break up. Ridiculously
>> huge AV sync values are shown in the OSD and frontend log.
>> - After seeking to the start and breaking sync it seems seeking forward
>> recovers sync.
>>
>> So am I the only one seeing this? If so, what is the magic config option
>> that I'm missing?
>
>
> I'm getting this too. �Playback data shows A/V sync generally at around
> +/-2. �Pausing/unpausing usually seems to fix it (A/V sync goes to something
> like 0.17). �Skipping makes it worse.
>
> I haven't been able to do too much playing around with it but it seems that
> even after pausing/unpausing, after a while I notice it's got out of sync a
> bit. �When I could check, I think A/V sync was showing around 1.x.
>
> I thought it might only be on HD/AC3 content but I think it happens on
> SD/MP2 stuff too. �All my recordings come in via DVB-S(2).
>
> At least the pause/unpause trick generally seems to work but it doesn't help
> the WAF when I have to do it several times during a recording (she doesn't
> seem to notice but it drives me up the wall!).
>
> Richard.
>
> _______________________________________________
> mythtv-users mailing list
> mythtv-users [at] mythtv
> http://www.mythtv.org/mailman/listinfo/mythtv-users
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lists at glidos

Jun 7, 2012, 3:23 PM

Post #5 of 33 (1633 views)
Permalink

Re: 0.25 Major AV sync problems [In reply to]

On 07/06/2012 23:11, Richard wrote:
> On 03/06/12 11:25, David Moore wrote:
>> Audio/Video sync has not been good for me ever since I upgraded to
>> 0.25. But since I haven't seen others complaining I wonder if I have a
>> config problem. Here's what I see:
>>
>> - OSD of Playback Data frequently shows A/V Sync values of around -2
>> and never "pulls in" to lower values without user intervention.
>> - Actual AV sync is not as bad as -2 seconds but is a large fraction
>> of a second.
>> - Seeking forwards or backwards almost always degrades AV sync.
>> - Pausing/unpausing usually, but not always, helps AV sync.
>> - Seeking back to the start of a recording loses sync for a few
>> seconds and sometimes never recovers. Audio and/or video may break up.
>> Ridiculously huge AV sync values are shown in the OSD and frontend log.
>> - After seeking to the start and breaking sync it seems seeking
>> forward recovers sync.
>>
>> So am I the only one seeing this? If so, what is the magic config
>> option that I'm missing?
>
> I'm getting this too. Playback data shows A/V sync generally at around
> +/-2. Pausing/unpausing usually seems to fix it (A/V sync goes to
> something like 0.17). Skipping makes it worse.

I've always had that with my systems: from 0.23 to 0.25 and various
hardware. Jumping back 5 secs fixes it for me.

Paul.
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dmoo1790 at ihug

Jun 7, 2012, 4:11 PM

Post #6 of 33 (1636 views)
Permalink

Re: 0.25 Major AV sync problems [In reply to]

Thanks for the confirmations that I'm not the only one seeing this
problem. FYI I have created a ticket #10797.
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peper03 at yahoo

Jun 8, 2012, 5:25 AM

Post #7 of 33 (1618 views)
Permalink

Re: 0.25 Major AV sync problems [In reply to]

On 08/06/12 01:11, David Moore wrote:
> Thanks for the confirmations that I'm not the only one seeing this
> problem. FYI I have created a ticket #10797.

I've done a little bit more testing but I can't say that I've managed to
home in on anything in particular.

I'm using an NVidia 8400GS card and sound output via the on-board Intel
chipset.

If I use the 'VDPAU Normal' profile, I get the problem. If I switch it
just 'Normal', everything seems to be ok (apart from not looking as nice).

With audio set to SPDIF, I get the problem. If I change audio to
analogue, I don't.

When I get the problem, the A/V sync value seems to stay pretty much
fixed (maybe a little bit of jitter in the hundredths range), changing
either the video or audio settings to stop the problem and it changes
almost constantly.

This is on my main box in the living room, running a fresh install of
Mythbuntu 12.04.

I cannot reproduce the problem on my desktop. It doesn't matter whether
what video or audio settings I use, everything stays in sync (I've no
way of listening to digital audio on the desktop but the A/V sync value
looks ok). Both machines have the same NVidia card in them (at least,
it's the same chipset), but the desktop machine does have slightly newer
NVidia drivers.

Here are the main differences:

Mythbox
-----------
NVidia 295.40
82801JI (ICH10 Family) HD Audio Controller
MythTV Version : v0.25.1

Desktop
-----------
NVidia 295.53
6 Series/C200 Series Chipset Family High Definition Audio Controller
MythTV Version : v0.25.1-1-g016db04

Does this give anyone any ideas?

Richard.

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steven at openmedia

Jun 17, 2012, 11:03 PM

Post #8 of 33 (1536 views)
Permalink

Re: 0.25 Major AV sync problems [In reply to]

On Sat, June 9, 2012 12:25 am, Richard wrote:
> On 08/06/12 01:11, David Moore wrote:
>> Thanks for the confirmations that I'm not the only one seeing this
>> problem. FYI I have created a ticket #10797.
>
> I've done a little bit more testing but I can't say that I've managed to
> home in on anything in particular.
>
> I'm using an NVidia 8400GS card and sound output via the on-board Intel
> chipset.
>
> If I use the 'VDPAU Normal' profile, I get the problem. If I switch it
> just 'Normal', everything seems to be ok (apart from not looking as nice).
>
> With audio set to SPDIF, I get the problem. If I change audio to
> analogue, I don't.
>
> When I get the problem, the A/V sync value seems to stay pretty much
> fixed (maybe a little bit of jitter in the hundredths range), changing
> either the video or audio settings to stop the problem and it changes
> almost constantly.
>
> This is on my main box in the living room, running a fresh install of
> Mythbuntu 12.04.
>
> I cannot reproduce the problem on my desktop. It doesn't matter whether
> what video or audio settings I use, everything stays in sync (I've no
> way of listening to digital audio on the desktop but the A/V sync value
> looks ok). Both machines have the same NVidia card in them (at least,
> it's the same chipset), but the desktop machine does have slightly newer
> NVidia drivers.
>
> Here are the main differences:
>
> Mythbox
> -----------
> NVidia 295.40
> 82801JI (ICH10 Family) HD Audio Controller
> MythTV Version : v0.25.1
>
> Desktop
> -----------
> NVidia 295.53
> 6 Series/C200 Series Chipset Family High Definition Audio Controller
> MythTV Version : v0.25.1-1-g016db04
>
>
> Does this give anyone any ideas?
>

I've upgraded from MythTV 0.23 to 0.25 and I'm seeing the issue on
existing as well as new DVB-S MPEG-2 recordings with MP2 audio.

I'm running a GT220 card with an M2NPV-VM board and an Athlon X2 5050BE CPU.

I noticed that my de-interlacers were disabled during the upgrade so I've
turned Advanced 2x back on. Display is generally 1920x1080 50Hz unless I'm
watching US content.

All my audio is going out over SPDIF to my amp. I haven't setup audio over
HDMI yet with the new upgrade.

In order to get any reasonable sync I need to exit playback and re-enter
the file. Otherwise its a real mess.

Steve

--------------------------------------------
Steven Ellis - Technical Director
OpenMedia Limited - The Home of myPVR
email - steven [at] openmedia
website - http://www.openmedia.co.nz
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steven at openmedia

Jun 18, 2012, 1:48 AM

Post #9 of 33 (1529 views)
Permalink

Re: 0.25 Major AV sync problems [In reply to]

On Mon, June 18, 2012 6:03 pm, Steven Ellis wrote:
>
> On Sat, June 9, 2012 12:25 am, Richard wrote:
>> On 08/06/12 01:11, David Moore wrote:
>>> Thanks for the confirmations that I'm not the only one seeing this
>>> problem. FYI I have created a ticket #10797.
>>
>> I've done a little bit more testing but I can't say that I've managed to
>> home in on anything in particular.
>>
>> I'm using an NVidia 8400GS card and sound output via the on-board Intel
>> chipset.
>>
>> If I use the 'VDPAU Normal' profile, I get the problem. If I switch it
>> just 'Normal', everything seems to be ok (apart from not looking as
>> nice).
>>
>> With audio set to SPDIF, I get the problem. If I change audio to
>> analogue, I don't.
>>
>> When I get the problem, the A/V sync value seems to stay pretty much
>> fixed (maybe a little bit of jitter in the hundredths range), changing
>> either the video or audio settings to stop the problem and it changes
>> almost constantly.
>>
>> This is on my main box in the living room, running a fresh install of
>> Mythbuntu 12.04.
>>
>> I cannot reproduce the problem on my desktop. It doesn't matter whether
>> what video or audio settings I use, everything stays in sync (I've no
>> way of listening to digital audio on the desktop but the A/V sync value
>> looks ok). Both machines have the same NVidia card in them (at least,
>> it's the same chipset), but the desktop machine does have slightly newer
>> NVidia drivers.
>>
>> Here are the main differences:
>>
>> Mythbox
>> -----------
>> NVidia 295.40
>> 82801JI (ICH10 Family) HD Audio Controller
>> MythTV Version : v0.25.1
>>
>> Desktop
>> -----------
>> NVidia 295.53
>> 6 Series/C200 Series Chipset Family High Definition Audio Controller
>> MythTV Version : v0.25.1-1-g016db04
>>
>>
>> Does this give anyone any ideas?
>>
>
>
> I've upgraded from MythTV 0.23 to 0.25 and I'm seeing the issue on
> existing as well as new DVB-S MPEG-2 recordings with MP2 audio.
>
> I'm running a GT220 card with an M2NPV-VM board and an Athlon X2 5050BE
> CPU.
>
> I noticed that my de-interlacers were disabled during the upgrade so I've
> turned Advanced 2x back on. Display is generally 1920x1080 50Hz unless I'm
> watching US content.
>
> All my audio is going out over SPDIF to my amp. I haven't setup audio over
> HDMI yet with the new upgrade.
>
> In order to get any reasonable sync I need to exit playback and re-enter
> the file. Otherwise its a real mess.

Ok I think I have a fix. Checking logs I saw the following alsa error

Jun 17 20:30:10 mythtv mythfrontend[20861]: E CoreContext
audio/audiooutputalsa.cpp:545 (OpenDevice) ALSA: Unable to sufficiently
increase ALSA hardware buffer size - underruns are likely

and recommendation

Jun 17 22:36:39 mythtv mythfrontend[26876]: E CoreContext
audio/audiooutputalsa.cpp:213 (SetPreallocBufferSize) ALSA: Try to
manually increase audio buffer with: echo 128 | sudo tee
/proc/asound/card0/pcm1p/sub0/prealloc

I've actually bumped the prealloc up a bit higher to be certain

echo 256 > /proc/asound/card0/pcm1p/sub0/prealloc

Just tested some files and sync is close to perfect and I'm not seeing any
audio centric errors.

Steve
--------------------------------------------
Steven Ellis - Technical Director
OpenMedia Limited - The Home of myPVR
email - steven [at] openmedia
website - http://www.openmedia.co.nz
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dmoo1790 at ihug

Jun 18, 2012, 2:56 AM

Post #10 of 33 (1531 views)
Permalink

Re: 0.25 Major AV sync problems [In reply to]

On 18/06/12 20:48, Steven Ellis wrote:
>
> On Mon, June 18, 2012 6:03 pm, Steven Ellis wrote:
>>
>> On Sat, June 9, 2012 12:25 am, Richard wrote:
>>> On 08/06/12 01:11, David Moore wrote:
>>>> Thanks for the confirmations that I'm not the only one seeing this
>>>> problem. FYI I have created a ticket #10797.
>>>
>>> I've done a little bit more testing but I can't say that I've managed to
>>> home in on anything in particular.
>>>
>>> I'm using an NVidia 8400GS card and sound output via the on-board Intel
>>> chipset.
>>>
>>> If I use the 'VDPAU Normal' profile, I get the problem. If I switch it
>>> just 'Normal', everything seems to be ok (apart from not looking as
>>> nice).
>>>
>>> With audio set to SPDIF, I get the problem. If I change audio to
>>> analogue, I don't.
>>>
>>> When I get the problem, the A/V sync value seems to stay pretty much
>>> fixed (maybe a little bit of jitter in the hundredths range), changing
>>> either the video or audio settings to stop the problem and it changes
>>> almost constantly.
>>>
>>> This is on my main box in the living room, running a fresh install of
>>> Mythbuntu 12.04.
>>>
>>> I cannot reproduce the problem on my desktop. It doesn't matter whether
>>> what video or audio settings I use, everything stays in sync (I've no
>>> way of listening to digital audio on the desktop but the A/V sync value
>>> looks ok). Both machines have the same NVidia card in them (at least,
>>> it's the same chipset), but the desktop machine does have slightly newer
>>> NVidia drivers.
>>>
>>> Here are the main differences:
>>>
>>> Mythbox
>>> -----------
>>> NVidia 295.40
>>> 82801JI (ICH10 Family) HD Audio Controller
>>> MythTV Version : v0.25.1
>>>
>>> Desktop
>>> -----------
>>> NVidia 295.53
>>> 6 Series/C200 Series Chipset Family High Definition Audio Controller
>>> MythTV Version : v0.25.1-1-g016db04
>>>
>>>
>>> Does this give anyone any ideas?
>>>
>>
>>
>> I've upgraded from MythTV 0.23 to 0.25 and I'm seeing the issue on
>> existing as well as new DVB-S MPEG-2 recordings with MP2 audio.
>>
>> I'm running a GT220 card with an M2NPV-VM board and an Athlon X2 5050BE
>> CPU.
>>
>> I noticed that my de-interlacers were disabled during the upgrade so I've
>> turned Advanced 2x back on. Display is generally 1920x1080 50Hz unless I'm
>> watching US content.
>>
>> All my audio is going out over SPDIF to my amp. I haven't setup audio over
>> HDMI yet with the new upgrade.
>>
>> In order to get any reasonable sync I need to exit playback and re-enter
>> the file. Otherwise its a real mess.
>
> Ok I think I have a fix. Checking logs I saw the following alsa error
>
> Jun 17 20:30:10 mythtv mythfrontend[20861]: E CoreContext
> audio/audiooutputalsa.cpp:545 (OpenDevice) ALSA: Unable to sufficiently
> increase ALSA hardware buffer size - underruns are likely
>
> and recommendation
>
> Jun 17 22:36:39 mythtv mythfrontend[26876]: E CoreContext
> audio/audiooutputalsa.cpp:213 (SetPreallocBufferSize) ALSA: Try to
> manually increase audio buffer with: echo 128 | sudo tee
> /proc/asound/card0/pcm1p/sub0/prealloc
>
> I've actually bumped the prealloc up a bit higher to be certain
>
> echo 256> /proc/asound/card0/pcm1p/sub0/prealloc
>
> Just tested some files and sync is close to perfect and I'm not seeing any
> audio centric errors.
>
> Steve
> --------------------------------------------
> Steven Ellis - Technical Director
> OpenMedia Limited - The Home of myPVR
> email - steven [at] openmedia
> website - http://www.openmedia.co.nz
>

Hi Steve, One of the first things I tried was increasing the ALSA buffer
size even though I wasn't getting the underrun warning. I raised the
ticket after I did this and I still get major sync loss when seeking
back to the start of a recording. Also minor (maybe a few tenths of a
second or less) unsync between audio and video when seeking forwards.
Pausing usually helps to improve sync.

The opinion of the person who analysed my logs was that the root problem
lies in ffmpeg code. From what little debugging I could do I tend to
agree. Haven't raised anything with ffmpeg devs yet. Not sure I have the
energy to take it further. Just living with it for now.
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jyavenard at gmail

Jun 18, 2012, 7:05 AM

Post #11 of 33 (1527 views)
Permalink

Re: 0.25 Major AV sync problems [In reply to]

Hi

On Monday, 18 June 2012, David Moore wrote:

>
>
> The opinion of the person who analysed my logs was that the root problem
> lies in ffmpeg code. From what little debugging I could do I tend to agree.
> Haven't raised anything with ffmpeg devs yet. Not sure I have the energy to
> take it further. Just living with it for now.
>
>
You could try upgrading to the current master.. It has a very recent
version of ffmpeg. and see if that helps...
Also,,try to,provide a sample in your ticket. So we can try to reproduce
your issue..

dmoo1790 at ihug

Jun 18, 2012, 6:41 PM

Post #12 of 33 (1514 views)
Permalink

Re: 0.25 Major AV sync problems [In reply to]

On 19/06/2012, at 2:05 AM, Jean-Yves Avenard <jyavenard [at] gmail> wrote:

> Hi
>
> On Monday, 18 June 2012, David Moore wrote:
>
>
> The opinion of the person who analysed my logs was that the root problem lies in ffmpeg code. From what little debugging I could do I tend to agree. Haven't raised anything with ffmpeg devs yet. Not sure I have the energy to take it further. Just living with it for now.
>
>
> You could try upgrading to the current master.. It has a very recent version of ffmpeg. and see if that helps...
> Also,,try to,provide a sample in your ticket. So we can try to reproduce your issue..
> _______________________________________________

Hi Jean-Yves, I'm running 0.25+fixes from mythbuntu repos. Is it possible to do a simple upgrade from this to the current master? Or do you mean compile the master from source?

I'll upload a sample when I can figure out where to upload it to. The things I see are common across all DVB-T broadcasts in NZ. No difference if I select AAC or AC3 audio on channels where this is possible. The problem seems to be something to do with audio PTS so I guess it's independent of codec type.

Not a huge problem for me now. I'm getting used to it. :) So don't let me divert you from more important work.

Cheers
David

jyavenard at gmail

Jun 18, 2012, 9:24 PM

Post #13 of 33 (1509 views)
Permalink

Re: 0.25 Major AV sync problems [In reply to]

On 18 June 2012 18:41, David Moore <dmoo1790 [at] ihug> wrote:

> Hi Jean-Yves, I'm running 0.25+fixes from mythbuntu repos. Is it possible to
> do a simple upgrade from this to the current master? Or do you mean compile
> the master from source?
Be aware that you will not be able to easily go back to 0.25+fixes,
and at best you'll have to go back to the last backup. So if you've
made any recordings after upgrading to master and you're going back to
0.25 they won't be easily accessible.

Having said that... There's a nightly build of master on the mythbuntu repo

>
> I'll upload a sample when I can figure out where to upload it to. The things
> I see are common across all DVB-T broadcasts in NZ. No difference if I
> select AAC or AC3 audio on channels where this is possible. The problem
> seems to be something to do with audio PTS so I guess it's independent of
> codec type.

it's bizarre that it's not something everyone would see
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bryan.bennetts at gmail

Jun 19, 2012, 1:02 AM

Post #14 of 33 (1507 views)
Permalink

Re: 0.25 Major AV sync problems [In reply to]

On 19 June 2012 05:24, Jean-Yves Avenard <jyavenard [at] gmail> wrote:

> it's bizarre that it's not something everyone would see

Ehm, I'm seeing similar symptoms (blushes, shuffles feet) haven't mentioned
it as there seemed to be others having a dig and once I'd shifted my audio
by 100ms it hasn't really bothered me, also I had done a fresh install to a
new FE using a different OS and upgraded myth version so there are an awful
lot of variables.

Separate BE/FE running Mythbuntu 0.25+fixes *although* I haven't updated
recently, > 2 weeks.

FE : Acer Aspire Revo r3700, audio out via spdif optical to Logitech Z-5500

UK DVB-t and t2 both seem to have the issue.

Likewise its a nice-to-fix but not imperative, I'm sure JY has alot more
intersting problems to look at :)

Cheers, Bryan.

dmoo1790 at ihug

Jun 19, 2012, 1:26 AM

Post #15 of 33 (1505 views)
Permalink

Re: 0.25 Major AV sync problems [In reply to]

On 19/06/12 16:24, Jean-Yves Avenard wrote:
> On 18 June 2012 18:41, David Moore<dmoo1790 [at] ihug> wrote:
>
>> Hi Jean-Yves, I'm running 0.25+fixes from mythbuntu repos. Is it possible to
>> do a simple upgrade from this to the current master? Or do you mean compile
>> the master from source?
> Be aware that you will not be able to easily go back to 0.25+fixes,
> and at best you'll have to go back to the last backup. So if you've
> made any recordings after upgrading to master and you're going back to
> 0.25 they won't be easily accessible.
>

I guess you mean the database schema is different in the master? Anyway
I probably won't try it. System is nearly perfect so don't want to risk
breaking it or making it worse.

>
> Having said that... There's a nightly build of master on the mythbuntu repo
>
>>
>> I'll upload a sample when I can figure out where to upload it to. The things
>> I see are common across all DVB-T broadcasts in NZ. No difference if I
>> select AAC or AC3 audio on channels where this is possible. The problem
>> seems to be something to do with audio PTS so I guess it's independent of
>> codec type.
>
> it's bizarre that it's not something everyone would see

More bizarre than you may think. I tried playing files with mythffplay
and also ffplay (version N-40644-g04064e1). Neither show the problems I
see in mythtv. One obvious difference is displayed A-V sync always
"pulls in" to a small value (< 0.1) with ffplay and mythffplay. With
mythtv it usually stops at a value around -2. Weird thing is
mythfrontend.real and mythffplay use the same libmythav* libraries.

And now that I grep the code for "AVSync" I find that mythplayer.cpp has
a bunch of functions which appear to handle audio/video sync. And there
appears to be different A/V sync code in ffplay.c. Hmmm. Starts to make
sense. I think the A/V sync code for any media player would likely be in
the player code rather than a shared library because it would be largely
codec independent. This would also explain why mythfrontend.real and
mythffplay can use the same libraries yet exhibit different A/V sync
behaviour.

So my bet is something in the mythplayer code is the problem, not in
ffmpeg code. Or maybe some interaction between mythplayer and ffmpeg code.

But once again let me stress that it would be nice to fix but not
critical for me. I can live with it.
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gnassas at mac

Jun 19, 2012, 9:29 AM

Post #16 of 33 (1499 views)
Permalink

Re: 0.25 Major AV sync problems [In reply to]

On 2012-06-19, at 4:26 AM, David Moore wrote:

> On 19/06/12 16:24, Jean-Yves Avenard wrote:
>>
>> it's bizarre that it's not something everyone would see
>
> And now that I grep the code for "AVSync" I find that mythplayer.cpp has a bunch of functions which appear to handle audio/video sync. And there appears to be different A/V sync code in ffplay.c. Hmmm. Starts to make sense. I think the A/V sync code for any media player would likely be in the player code rather than a shared library because it would be largely codec independent. This would also explain why mythfrontend.real and mythffplay can use the same libraries yet exhibit different A/V sync behaviour.

To add another datapoint I see major A/V sync problems with HLS streams - when someone on camera is speaking their lips are nowhere near their words. I don't have a good sense of when it started happening but I'm pretty sure it was after the post-.25 ffmpeg sync.

- George
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J.Pilk at tesco

Jun 19, 2012, 11:12 AM

Post #17 of 33 (1494 views)
Permalink

Re: 0.25 Major AV sync problems [In reply to]

On 19/06/12 17:29, George Nassas wrote:
> On 2012-06-19, at 4:26 AM, David Moore wrote:
>
>> On 19/06/12 16:24, Jean-Yves Avenard wrote:
>>>
>>> it's bizarre that it's not something everyone would see
>>
>> And now that I grep the code for "AVSync" I find that mythplayer.cpp has a bunch of functions which appear to handle audio/video sync. And there appears to be different A/V sync code in ffplay.c. Hmmm. Starts to make sense. I think the A/V sync code for any media player would likely be in the player code rather than a shared library because it would be largely codec independent. This would also explain why mythfrontend.real and mythffplay can use the same libraries yet exhibit different A/V sync behaviour.
>
> To add another datapoint I see major A/V sync problems with HLS streams - when someone on camera is speaking their lips are nowhere near their words. I don't have a good sense of when it started happening but I'm pretty sure it was after the post-.25 ffmpeg sync.
>
> - George

Hi: I haven't seen the sync problem. I still have 0.24.3 and an ageing
0.25-fixes. But I do see the error message:

Try to manually increase audio buffer with: echo 128 | sudo tee
/proc/asound/card0/pcm0p/sub0/prealloc

In Fedora I don't use sudo, but the reports stop if I do it as su.
It doesn't survive a reboot. Can I do that?

TIA,

John P
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gary.buhrmaster at gmail

Jun 19, 2012, 12:47 PM

Post #18 of 33 (1493 views)
Permalink

Re: 0.25 Major AV sync problems [In reply to]

On Tue, Jun 19, 2012 at 6:12 PM, John Pilkington <J.Pilk [at] tesco> wrote:
....
> In Fedora I don't use sudo, but the reports stop if I do it as su.
> It doesn't survive a reboot. �Can I do that?

One should try to never run the frontend as the root user
(and once one does, some files may get modified in
such a way that fixups will need to be manually taken
to correct ownership/permissions before being able
to run as the mythtv user; if you decide on running as
root, always run as root).

The *usual* suggestion is to place your mythtv frontend
user in the audio/video groups, or to write udev rules to allow
the frontend user the appropriate permissions. One can
also create /etc/rc.local and include commands such
as setting buffers, permissions, etc.

Gary
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J.Pilk at tesco

Jun 19, 2012, 1:15 PM

Post #19 of 33 (1493 views)
Permalink

Re: 0.25 Major AV sync problems [In reply to]

On 19/06/12 20:47, Gary Buhrmaster wrote:
> On Tue, Jun 19, 2012 at 6:12 PM, John Pilkington<J.Pilk [at] tesco> wrote:
> ....
>> In Fedora I don't use sudo, but the reports stop if I do it as su.
>> It doesn't survive a reboot. Can I do that?
>
> One should try to never run the frontend as the root user
> (and once one does, some files may get modified in
> such a way that fixups will need to be manually taken
> to correct ownership/permissions before being able
> to run as the mythtv user; if you decide on running as
> root, always run as root).
>
> The *usual* suggestion is to place your mythtv frontend
> user in the audio/video groups, or to write udev rules to allow
> the frontend user the appropriate permissions. One can
> also create /etc/rc.local and include commands such
> as setting buffers, permissions, etc.
>
> Gary

Thanks, Gary. I didn't mean I was running myth as root, just issuing
that command from a konsole as root with mythfrontend already running:

su
<give password>
echo 128 | tee /proc/asound/card0/pcm0p/sub0/prealloc
exit

and my question was, I hope, can I do that permanently?

John
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jyavenard at gmail

Jun 19, 2012, 2:03 PM

Post #20 of 33 (1499 views)
Permalink

Re: 0.25 Major AV sync problems [In reply to]

On 19 June 2012 01:02, Bryan Bennetts <bryan.bennetts [at] gmail> wrote:

> Ehm, I'm seeing similar symptoms (blushes, shuffles feet) haven't mentioned
> it as there seemed to be others having a dig and once I'd shifted my audio
> by 100ms it hasn't really bothered me, also I had done a fresh install to a
> new FE using a different OS and upgraded myth version so there are an awful
> lot of variables.

A fixed delay is an entirely different matter and is something that
can't be avoided as hardware along the way introduce delays...

This is what the A/V delay settings is for.
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jyavenard at gmail

Jun 19, 2012, 2:05 PM

Post #21 of 33 (1489 views)
Permalink

Re: 0.25 Major AV sync problems [In reply to]

On 19 June 2012 09:29, George Nassas <gnassas [at] mac> wrote:

> To add another datapoint I see major A/V sync problems with HLS streams - when someone on camera is speaking their lips are nowhere near their words. I don't have a good sense of when it started happening �but I'm pretty sure it was after the post-.25 ffmpeg sync.

Which version are you referring to ?
Myth 0.25 doesn't play HLS streams...

So I don't see how it could have broken A/V sync for playing HLS stream...
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jyavenard at gmail

Jun 19, 2012, 2:07 PM

Post #22 of 33 (1496 views)
Permalink

Re: 0.25 Major AV sync problems [In reply to]

On 19 June 2012 13:15, John Pilkington <J.Pilk [at] tesco> wrote:
>
> and my question was, I hope, can I do that permanently?

Put it in /etc/rc.local script

That's what it's for...
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mythtv at moasat

Jun 19, 2012, 6:43 PM

Post #23 of 33 (1484 views)
Permalink

Re: 0.25 Major AV sync problems [In reply to]

> -----Original Message-----
> From: mythtv-users-bounces [at] mythtv [mailto:mythtv-users-
> bounces [at] mythtv] On Behalf Of Jean-Yves Avenard
> Sent: Monday, June 18, 2012 11:25 PM
> To: Discussion about MythTV
> Subject: Re: [mythtv-users] 0.25 Major AV sync problems
>
> it's bizarre that it's not something everyone would see

I've had A/V sync issues since 0.24. I never spent the time to narrow it
down to either myth or HD-PVR.

I keep expecting the next version of Myth to finally fix it but so far it
hasn't.

Playing back A/V is not a trivial thing though so I know how hard it is to
get right across multiple hardware platforms and multiple AV formats.

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gnassas at mac

Jun 19, 2012, 9:40 PM

Post #24 of 33 (1485 views)
Permalink

Re: 0.25 Major AV sync problems [In reply to]

On 2012-06-19, at 5:05 PM, Jean-Yves Avenard wrote:

> On 19 June 2012 09:29, George Nassas <gnassas [at] mac> wrote:
>
>> To add another datapoint I see major A/V sync problems with HLS streams - when someone on camera is speaking their lips are nowhere near their words. I don't have a good sense of when it started happening but I'm pretty sure it was after the post-.25 ffmpeg sync.
>
> Which version are you referring to ?
> Myth 0.25 doesn't play HLS streams...
>
> So I don't see how it could have broken A/V sync for playing HLS stream...

Whoops, I'm talking about the other side. I see sync probs watching HLS streams created by myth and viewed in OSX/Safari and iOS/Safari. The reason I spoke up is David's comment about how the problem was present in some players and not others. If you take mythtranscode's decode half as a player it falls into the problem category and might give you an easy way to figure out the issue. Or not. Just tossing it out there.

As for version I'm on master v0.26-pre-519-g48c9f6e-dirty, the dirtyness comes from running the two ticket patches I filed recently (bonjour service name, video metadata thread safety). Where it counts it's stock recent git master.

- George
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lists at glidos

Jun 19, 2012, 11:56 PM

Post #25 of 33 (1490 views)
Permalink

Re: 0.25 Major AV sync problems [In reply to]

George Nassas <gnassas [at] mac> wrote:

>On 2012-06-19, at 5:05 PM, Jean-Yves Avenard wrote:
>
>> On 19 June 2012 09:29, George Nassas <gnassas [at] mac> wrote:
>, I'm talking about the other side. I see sync probs watching HLS
>streams created by myth and viewed in OSX/Safari and iOS/Safari.

I see exactly the opposite to that. All my recordings and almost all my transcodes (made by mythtranscode in fifo mode) play perfectly in other players. It is only mythfrontend where I have sync problems. And I always have had, even back at 0.23. On occasion I've had transcodes produced with sync problems, but then the sync has been miles out, so clearly a different problem.

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