capturing analog-tv > divx is out of a/v-synch

[servass]

capturing with divx on the fly via soundcard is always progressivly out of synch. hardware is strong enough (20% cpu).
has anyone solved this problem?

[chipzoller]

What program are you using to capture? How is your audio connected in this process? More info. all around, please.

But to begin with, make sure when you're capturing with DivX you're doing so at an appropriate level for on-the-fly compression. Check by looking at CPU usage while capturing. If it's 100% (you said 20%, but I don't know if this is while capturing compressed) it's likely you're dropping frames.

[servass]

programms: wintv2k, virtualdub, iuvcr.
codec: divx 6.xx, xvid,
cpu while capturing and encoding: 20 % use. (dual core, AMD 4600 X 2. 40% AMD 3000+).
sound: onboard or soundcard (creativ) .
mainboard: asus. different types.
tv-card: hauppauge-pci. different types. analog.
hdd: sata, ide. fast enough. not fragmented.

dropped frames? maybe but improbably. how can I check if frames dropped?

It seems it's an inherent problem and has in my case nothing to do with to littly power or driver. so, its unsolved. try it and you have this problem with softencoding even you have enough power, independently on your hard- or software. after 30 min... 60 min a/v-non-synch is visible.

sometimes in forums there are a/v problems with encoding from dvd....

[chipzoller]

Is the analogue audio connected to the audio in of your sound card? If so after 30 or more minutes an a/v sync can be apparent because there is no way for the clocks to completely synchronize. If your card has WDM drivers, you should try VirtualVCR and check "resample audio dynamically" under 'AV Sync'. This will normally fix the syncing issues. And I would recommend capturing via a lossless codec like HuffYUV first then to DivX later as you generally get better quality and faster captures.

[servass]

ok, different clock's cause different times. it seems logical to me.

VirtualVCR and check "resample audio dynamically" under 'AV Sync' - I can't find this menuepoint on VirtualVCR 4.11. please give me a little bit more advice. thx

p.s.: I have wcm-driver in use. no vfW.
Hauppauge WinTV 878/9 WDM Aux Driver

[chipzoller]

Under the 'A/V Sync' tab.
VirtualVCR 4.11
Do you mean v2.6.9 (http://virtualvcr.sourceforge.net/html/virtualvcr/download.php)?

[FishTank]

i do xvid capture on the fly all the time.

do you capture the sound as PCM or mp3 ?
because i never have sync probs with uncompressed audio and
compressed video, but as soon as i try both, all hell breaks loose lol

[servass]

Under the 'A/V Sync' tab.

Do you mean v2.6.9 (http://virtualvcr.sourceforge.net/html/virtualvcr/download.php)?

sorry, I tried http://www.virtualdvr.com/ :D
now, I will try virtualvcr...


do you know, what does "resample audio dynamically" mean?
if two different clocks in use, how can one synch this timings? because there is no connection between this clocks, only the human beeing that looks at the video .... ?

[FishTank]

silly question, but that would mean that its actually better to
use the audio line in on the capture card (i have an external one)
compared to the line in on the sound card.

im just asking, because i read somewhere that the quality would
be better if you use the soundcard (as its mostly superior to the capture card soundwise).
if you have to deal with out of sync sound then id prefer to use
the capture cards soundchip lol.

(dont mean to hijack your topic btw. sorry)

[chipzoller]

that would mean that its actually better to
use the audio line in on the capture card (i have an external one)
compared to the line in on the sound card.
Not exactly. Some lower-end model capture cards don't have a good A/V clock sync, so the longer your capture goes the more likely it will be just slightly out of sync. And if audio is captured through your sound card, only after these long captures is the audio slightly out of sync...we're talking fractions of seconds usually.

do you know, what does "resample audio dynamically" mean?
Resample audio dynamically means that because there is no hardware clock sync for the two lines, the program will automatically increase or decrease the audio sample rate (thus slightly slowing or speeding up the rate of the audio) to compensate for this to ensure the two streams are as close as possible. As as I mentioned above, the longer the capture, usually the more resampling has to be done, but even at that the change is not noticible.

For more info. about this process, read this (http://virtualvcr.sourceforge.net/html/virtualvcr/sync.php).