Skip causes replay with AVIs on MVP

[dvasco]

This is an intermittent problem. When watching AVIs and trying to skip ahead the AVI will actually jump back in time. Then when I try to jump ahead it will sometimes go to where I was and sometimes go back even farther. On one show it would never go to a certain portion I was trying to access, even after jumping past it then trying to go back. I had an option of sitting through a boring part or just not watching that portion. I tried a higher bitrate of 4000 for ffmpeg but that didn't help. Is there a setting in ffmpeg that would help with this? Isn't there something like I,B, and F frames or similar for mpegs?

[SuMo]

... Isn't there something like I,B, and F frames or similar for mpegs?

??? euhhh I don't think I understand correctly but in case I do, mpegs are always made out of gops, who are made of I, B and P frames. One exeption, there are I-frame only mpeg streams.

Doesn't answer your question but can it be you're trying to skip to a part of the avi that hasn't been transcoded to mpg for MVP playback at that time?

[zehd]

This is an intermittent problem. When watching AVIs and trying to skip ahead the AVI will actually jump back in time. Then when I try to jump ahead it will sometimes go to where I was and sometimes go back even farther. On one show it would never go to a certain portion I was trying to access, even after jumping past it then trying to go back. I had an option of sitting through a boring part or just not watching that portion. I tried a higher bitrate of 4000 for ffmpeg but that didn't help. Is there a setting in ffmpeg that would help with this? Isn't there something like I,B, and F frames or similar for mpegs?

I have been dealing with that for a while. It seems that with any of the three Transcoders I tried, and in many configurations of bitrate, dimensions, Key Interval (which deals with the IFrame you talked about), some AVI just won't act nicely.

To recap, you're not actually viewing a AVI when you're watching your show. It must be transcoded onthe fly to MPG format. That transcode process is where the trouble comes in...

Sub has mentioned that he noticed the time line generated in the transcoded MPGs is not as accurate as an MPG created while recording live TV using the hardware encoders of a tuner card.

It's something that we may have to live with until a transcoder comes along that can transcode on the fly (which means QUICKLY) and can be easily integrated into the transcode process.

Currently GB-PVR uses FFmpeg that ships with it. Sub has written in hooks for other apps to Transcode, ZProcess for example, will let you choose between FFmpeg, MEncoder, and VLC as transcode processors.

This is a long answer to saying: right now, it's not gonna work right...

[dvasco]

mpegs are always made out of gops, who are made of I, B and P frames.

That is what I wanted to know.

Doesn't answer your question but can it be you're trying to skip to a part of the avi that hasn't been transcoded to mpg for MVP playback at that time?

No.

[dvasco]

I have been dealing with that for a while. It seems that with any of the three Transcoders I tried, and in many configurations of bitrate, dimensions, Key Interval (which deals with the IFrame you talked about), some AVI just won't act nicely.



Sub has mentioned that he noticed the time line generated in the transcoded MPGs is not as accurate as an MPG created while recording live TV using the hardware encoders of a tuner card.

It's something that we may have to live with until a transcoder comes along that can transcode on the fly (which means QUICKLY) and can be easily integrated into the transcode process.

Currently GB-PVR uses FFmpeg that ships with it. Sub has written in hooks for other apps to Transcode, ZProcess for example, will let you choose between FFmpeg, MEncoder, and VLC as transcode processors.

This is a long answer to saying: right now, it's not gonna work right...

Darn. How about using quickstream fix from VideoRedo? Or a reencoder like Rejig?

By the way, thanks for supplying the long answer and explanation.

[zehd]

Darn. How about using quickstream fix from VideoRedo? Or a reencoder like Rejig?

By the way, thanks for supplying the long answer and explanation.

If you are able to take an AVI or MPG and reencode it so that the skiprw/ff works right AND it can be done faster than real time (at least 50% faster) than I wanna know...

What I meant by 50 % faster is:

When GB-PVR calls a transcoder, the transcoder starts up and starts creating a file. GB-PVR gives the transcoder a head start, maybe 5.5 secs (default) or more. Then it starts to play the file that is being transcoded...

A common problem is that GB-PVR runs out of file to playback and crashes, because the transcoder was too slow.

A very basic benchmark that I use is 'How long does it take the transcoder to transcode 1 min of video if a transcode could transcode code...'

If you can get that 1 min done in around 30-40 secs or less, I wanna know...

[dvasco]

I know that VideoRedo Quickstream and Rejig are faster than realtime. I have never timed it to see if 50% or less. VideoRedo Quickstream fixes mpegs and Rejig is a transcoder and not a true reencoder like TMPGenc. No matter what I was throwing it out there as an idea. Just wishful thinking.

[mvallevand]

A common problem is that GB-PVR runs out of file to playback and crashes, because the transcoder was too slow.

It's not just transcoding its the whole process of transcoding, the bit rate chosen and the reading/writing/reading from disk followed by the streaming to the mvp. Also resizing is intensive too and it is sometimes better to let the mvp do it in hardware.

One of the features of mvpmc is direct control of vlc (via a remote control interface). It is too technical to setup for most people, it even confuses many hardcore linux users, and I won't elaborate here, but just to have vlc transcode from file to an http stream I can see from 15% to 90% CPU use for the same file depending on the transcoding options selected.

Martin