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intermittent audio jitter / echo
http://forum.linhes.org/viewtopic.php?f=6&t=6621		 Page 1 of 1
Author:  SlyOne [ Tue Oct 25, 2005 6:31 pm ]
Post subject:  intermittent audio jitter / echo
Since I upgraded to R5A22 I have been getting a strange intermittent audio jitter. It is like the audio jumps forward and back playing over itself several times. It seems to happen worse after a short while playing, but will eventually start behaving again. It's not just on the playback and live tv. I tried cating the /dev/video0 to a file and playing it on both the mythfrontend and also on my windows laptop. It stutters in exactly the same place. I took a sample of the audio so you can hear the type of problem.

Download Sample 2.6MB

I tried installing the TV card in a completely different machine with a fresh install but it does the same.

The system specs of the two systems I have tried are:
1:
ABIT KT7A MB with 1GHz Athlon XP
PVR-250
Soundblaster Live sound card

2:
Dell Dimention 8100
PVR-250
Soundblaster Live Sound card (Different one to above)

The PVR 250 card shows up in lspci as:
Internext Compression Inc iTVC16 (CX23416) MPEG-2 Encoder (rev 01)

It is a UK model one.

if I grep dmsg for tuner I get:
Code:
tuner (ivtv): chip found at addr 0xc2 i2c-bus ivtv i2c driver #0
ivtv0: i2c attach to card #0 ok [client=(tuner unset), addr=61]
tveeprom: tuner = Philips FI1246 MK2 (idx = 11, type = 1)
tveeprom: tuner fmt = PAL(I) (eeprom = 0x10, v4l2 = 0x00000010)
tuner: type set to 1 (Philips PAL_I (FI1246 and compatibles)) by ivtv i2c driver #0


Could an incorrect tuner type be causing the jitter?
Author:  parkinpants [ Thu Oct 27, 2005 3:06 am ]
Post subject:  audio buffering
have you tried enabling extra audio buffering?
Author:  SlyOne [ Thu Oct 27, 2005 3:39 pm ]
Post subject: 
yes, it makes no difference.
Author:  SlyOne [ Fri Oct 28, 2005 6:47 pm ]
Post subject: 
if I change the tuner type in /etc/mythtv/modules/ivtv to type 5 (the default detected is type 1) I loose the echo effect, but the recording stutters instead. Type 45 seems to be working better so far, but I have only just started testing it.

Does anyone know what I should actually have the tuner type set to for this machine, and this card type?
Author:  SlyOne [ Fri Oct 28, 2005 7:08 pm ]
Post subject: 
Damn, spoke to soon, it's started doing it again :(

It's wierd the way it is not consistent, it seems to get worse at times, sometimes it is fine. Usually gets bad just as a good bit is comming up, but I guess that is just sod's law in action.

Full lspci shows the card as:
Code:
0000:02:08.0 Multimedia video controller: Internext Compression Inc iTVC16 (CX23416) MPEG-2 Encoder (rev 01)
        Subsystem: Hauppauge computer works Inc. WinTV PVR 250
        Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV+ VGASnoop- ParErr- Stepping- SERR+ FastB2B-
        Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR-
        Latency: 64 (32000ns min, 2000ns max), Cache Line Size: 0x10 (64 bytes)
        Interrupt: pin A routed to IRQ 19
        Region 0: Memory at d8000000 (32-bit, prefetchable) [size=64M]
        Capabilities: [44] Power Management version 2
                Flags: PMEClk- DSI- D1- D2- AuxCurrent=0mA PME(D0-,D1-,D2-,D3hot-,D3cold-)
                Status: D0 PME-Enable- DSel=0 DScale=0 PME-
Author:  aclose [ Mon Oct 31, 2005 8:51 pm ]
Post subject: 
hmm, i think i've got the same problem. i just upgraded from R5A16 to R5A22 and am now getting the stuttering in audio playback.
however, i did change a couple of the default settings during the upgrade. i just noticed that one recording that was default appears to have turned out ok. the one i just got done watching that was 'high quality' was stuttering. so i'm having a look at my recording settings, audio & video.
Author:  gravety [ Wed Nov 02, 2005 3:43 am ]
Post subject: 
I have noticed this too. Sometimes TV plays fine and then others the audio is really poor, cracky and stutters.

I also get this when playing back XviD in MythVideo as well. Sometimes they play back fine and sometimes I have to exit then re-play the file!

I have uninstalled alsa and re-compiled it with the latest. I have always had to do this with KnoppMyth as if I don't everything goes haywire when trying to time search forward/backward (in anything!)...
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