mpegplayer A/V sync - please report experiences

[linuxstb]

Yes, linuxstb described it as a requirement for this test and I think that it is obvious.

In addition the "Show FPS" option does not work on H120. Is it supposed to work on greyscale targets?

mpegplayer on greyscale targets is very early and no optimisations have yet been made - so it's too slow to play anything in realtime at the moment, meaning a/v sync is impossible.  Work may happen to improve it, but like anything, it depends on a developer taking an interest and doing the work.

Also, I think all the devs agree that "rvf" format playback (the same Rockbox-specific format used on the old Archos devices) will provide better performance than mpegplayer on greyscale targets.  This performs the conversion to the format required by the greyscale lib in advance (on your PC), and Rockbox just needs to blit the frames to the LCD at the required speed - no decoding.  However, the downside is that the files will be around 1.8Mbit/s, compared to around 300kbit/s for the equivalent sized mpeg file.

[linuxstb]

Have to say that before improvements my quality video in MpegPlayer on IPOD nano was perfect and A/V sync works wonderfully. But after this it became worse, especially video. So please do feedback.

If you want to help me fix it, please provide a sample file.  Otherwise, there's nothing I can do.

[Llorean]

And with the sample file, you should also explain what "worse" behaviour you're having.

[Didro]

And with the sample file, you should also explain what "worse" behaviour you're having.

Video is not so smooth, looks like it skips to many frames.

[Didro]

I tried to set off Skip Frames option: video became good. Besides that A/V sync is good too in many videos but in other audio goes ahead video.

[linuxstb]

I tried to set off Skip Frames option: video became good. Besides that A/V sync is good too in many videos but in other audio goes ahead video.

Didro,

Can you upload your video somewhere for me to analyse?

[Amblin]

So far, I have tried a number of files, from different sources, all encoded from different codecs like XVID and DIVX, with 2 different programs, TMPEG 4.0 and
recently WinFF. It seems to me that at the beginning of each file, after about 5 seconds, the plugin skips forward 2-3 seconds of audio and stays that way for the remainder of the video.

[Llorean]

Again, he needs a sample video where this doesn't occur playing the video on the PC, but does on the device.

As you may have guessed, problems that are readily apparent don't happen with the video's he's encoded (and that skipping after 5 seconds hasn't happened with any I've encoded) so just describing the bug isn't necessarily enough information.

If that happens then you should just need to encode a 20 second video or so to demonstrate it. Also, of course, it's expected that you're testing on unmodified official Current Builds

[Amblin]

Ok, Ive had a breakthrough. On both WinFF and TMPEG 4, if I manipulate the screen ratio (16:9 to 4:3 for example) on a clip, the A/V will play in sync on my computer but not on the plugin. If I choose to leave the ratio alone, the A/V will play in sync on the plugin just fine. This issue has also come about when converting clips for the OF's video player. Its beyond me why something like changing the screen ratio would affect sound, but some of you more tech people should know..

[linuxstb]

Amblin,

I can't replicate your problems with my own files - can you give me a copy of a video you've encoded that plays correctly on your PC, but not in Rockbox?

[Didro]

Insert Quote    
Quote from: Didro on March 28, 2007, 05:46:41 AM

I tried to set off Skip Frames option: video became good. Besides that A/V sync is good too in many videos but in other audio goes ahead video.



Didro,

Can you upload your video somewhere for me to analyse?

linuxstb, here is uploaded video in which audio goes ahead video on my iPOD nano:

http://www.sendspace.com/file/ixc5z1 (10 MB)

[Llorean]

Okay, on my Nano, the audio and video stay in sync just fine, it just drops a LOT of frames. More than it does if I try it with an older build (I had an older build on the first time I tried the file, sadly I'm not sure what build it was).

With both builds I reached the end of the file and it was in sync even at the very end. It may be that the framedropping is making it look like it's out of sync to you, or there may be a communication issue in regards to terms.

Are you seeing the video pause for about a half a second, but the audio continues, then the video skips ahead a very little bit to where the sound is, but the sound immediately continues ahead without the video again?

[Didro]

Okay, on my Nano, the audio and video stay in sync just fine, it just drops a LOT of frames.

I have such situation too, and to make video smooth without skipping so many frames i set off Skip Frames option. Then video became good, and even A/V sync became good in some videos, but in other A/V sync is bad, and in my opinion for Nanos new improvement isnt good, cause before it video and A/V sync was nice but now...  

[Llorean]

If you turn off Skip Frames, it can't sync the Audio and Video. Any time they line up is luck.

Was your bad A/V sync always with it off?

[Didro]

If you turn off Skip Frames, it can't sync the Audio and Video. Any time they line up is luck.

Was your bad A/V sync always with it off?

I dont know, but A/V sync keeps normal in many videos. Maybe I just encode video with suitable FPS, video and audio bitrate.
Also have to say that with new improvements I can run only one video succesfully, when I run next it makes screen black and only audio plays so to view it I must reboot rockbox. Before mpegplayer hangs not so often.