Power Supply problems & a/v mismatch

[Mk4ever]

Hello,

In another forum, a guy asked about how to overcome a/v mismatch problem during video encoding. A moderator there replied that one of the possibilities is a weak power supply !

Oh ! and among the causes he mentioned is a slow PC, AND a slow HDD (he mentioned something about 7200 vs. 5400 RPM!).

As far as I know, this can't be true and it doesn't even make sense. A bad power supply could affect stability and/or cause other problems but to only produce a problem of a/v mismatch during encoding is impossible.

I wanted to reply but I wanna make sure I'm right before posting.

Can you guys give me your opinions or ideas?

[Guest]

The guy is clueless. Ask him to explain exactly how the power supply could cause an AV mismatch.

[Mk4ever]

Not only he said what he said, but he also insists that he had a/v mismatch during encoding and when he changed the power supply it disappeared!

In Arabic forums, everyone lives for rumors and non-sense. I wanna be the logical guy. But the argument is so obvious and basic that I don't know from where to start or what logic to use to convince him !

[Guest]

That why I suggested that you ask him to provide an explanation of the exact mechanism.

Your comment on Arabic sites is rather un-PC. I would avoid that kind of rhetoric if I were you.

[Mk4ever]

The problem is, I am trying to explain to them about video, audio, playback and encoding. Most of them can't manage to read and understand English correctly.

So just like the way you guys teach us, I try to return the favor and teach someone else.

This is my problem !

Anyways thank you very much. and truly I'm glad that someday I had a little chat with neuron2 :)

[Guest]

I'm glad that someday I had a little chat with neuron2 Hey, I'm just a normal guy. You can chat with me any time!

[morph166955]

The only thing I can think of that would even remotely cause a problem is if your power supply was being overrun by your system needs (eg a 300W PS and the system wants 350W or something like that) and that the system is some how malfunctioning from a power drop. This however is EXTREMELY (let me say that again) EXTREMELY unlikely event because in that case the PS would probably just shut itself down or the system would lock up or shut down or everything else not just A/V would become very unstable or something else similar to that. Can you give us more details about your system? please be as specific as possible, giving model #'s and such is probably sufficient unless you have something very random and hard to find info on then a few details on specs would be great. Also some info about your source (bitrate, size, fps, codec, etc) would be great. But again, most likely, its NOT your power supply.

As for hard drive and cpu speeds like you mentioned, that does come in the realm of possible. If the drive cant supply the file to the computer fast enough you do run the risk of getting an A/V mismatch/desync since it may be doing the audio at a faster/slower rate then the video. Something you could try is to use ffdshow and enable the OSD to show you some info on whats going on in the decoder itself. Specifically, cpu load, decoder fps, and time on ffdshow are great ways to see whats going on. You can see if your cpu is just not fast enough (pegged cpu load) easily with that. If the decoder fps is less then the movies fps, then its obvious that it wont be able to display the movie properly. I see this on one of my older media centers when playing 720p content. It starts out good but in a higher action scene my decoder fps drops to ~21fps (the media is at 24fps). The audio decodes with out any issues since thats small and running in a different thread on the cpu, but the video is only outputing at 21fps so I get a slow desync happening. the same media on a newer media center decodes at more then 24fps so I dont get the issues there. What the guy who said it could be your PS may not have realized is that if his PS was undersized for his system and his system was starved for power, it could have slowed itself down to protect itself thus causing his desync. A new PS "COULD" then have supplied enough power to his system for it to achieve the processing power necessary to decode the video fast enough to not desync.

[Blue_MiSfit]

For decoding, I would totally agree. However for encoding, where real-time is not an issue, I don't think the power supply would have any impact on sync.

~Misfit

[morph166955]

I agree. I would love to know if the same video does play properly on another (preferably newer and faster) system or if it is also desynced. Also more information on the nature of the desync/mismatch would be helpful.

[Lenny_Nero]

I have seen many a PSU that is having problems cause some very strange things, that looked at first to be nothing to do with power, and I for one would never say that there is no chance of one on its last legs, or being pushed over its limits and sending all manor of ripples and odd voltage spikes. But I agree that this might be pushing it a bit, unless there are other problems, or its over clocked and the CPU is having problems keeping up with the load.

As said it could be more lightly that the CPU is getting loaded, or the media player could be to 'heavy'. I have just been helping someone out that could not get windows media player to work properly and was using >50% of the processor and because of the other things he was doing it was all too much. I gave him Media Player Classic and it can do it ok, if he is not silly with all of the other stuff he often has running.