understanding transcoding

[cakes]

When going through the wiki and the forum, it seams that I missed something.
In the config app, there are two options regarding transcoding and the MVP: use ffmpeg & use ffdshow.
- why would you use ffmpeg?
- why would you use ffdshow?
- does it make sense to use both ffmpeg & ffdshow?
- if you uncheck both options, which module does the transcoding then? gppvrconvert.exe?


Thanks,
Cakes

[cakes]

After going through at least part of the AVI and MVP thread, It is getting clearer to me. I tried to formulate what I learned in a way that I would have liked in the documentation on configuration (instead of working myself through a 17 page thread..... ).

In the playback tab, there are two checbox that control the way GBPVR transcodes AVI movies:
- use ffdshow with transcode
- use FFmpeg for transcode

1. If you uncheck both options, transcodeing is performed by Trans2MVP.exe, which is only a small wrapper for the Hauppauge transcoding components. This method works for most avi's but has the same limitations as the MVP software has:
- the MVP can only correctly display certain resolution videos.
- some video's are shown with one big black bar below the screen.
- ...
2. Checking ffdshow will use ffdshow for transcoding. ffdshow is a general purpose divx/xvid decoder and packed together in the standard gbpvr installation file. ffdshow gives the opportunity to resize non-standard videos to a size that can be displayed cleanly on the MVP. Tweaking this transcoding can be done in config.xml

3. Checking ffmpeg wil use ffmpeg for transcoding.
<sorry, I still didn't figure out why to use ffmpeg...>

If this description is fine, how to get it in the wiki?

[sub]

The ffmpeg option is as alternative to using Trans2MVP.exe. ffmpeg uses slightly less CPU, and has been a little more reliable for most people because it has no dependencies on the combinations of directshow filters installed on the users machine.

The ffdshow option only applies when you're using trans2mvp.

[cakes]

and what happens if you check both the ffdshow and ffmpeg option?

[sub]

then it'll use ffmpeg but not ffdshow, since that is only used when using trans2mvp

[blader_se]

If this description is fine, how to get it in the wiki?

Just PM me to be added to the wiki user list...

[IgiLama]

If I understand it correctly because of used transcoding solution it is impossible to seek thru video file beyond already transcoded part. So I can't jump to the half of a movie in beginning. I have to wait for transcoder to get there. Is that right? And if it is, is there some workaround to make it possible? For example to use some frameserving :confused:

[sub]

If I understand it correctly because of used transcoding solution it is impossible to seek thru video file beyond already transcoded part. So I can't jump to the half of a movie in beginning. I have to wait for transcoder to get there. Is that right?

Correct. This is a good reason to leave your recordings as MPEG2 files if you use an MVP.

And if it is, is there some workaround to make it possible?

No.

[IgiLama]

This is a good reason to leave your recordings as MPEG2 files if you use an MVP.

So MPEG2 files are streamed directly!? Why others can't be? Say transcoded "on-the-fly" (streamserved). Avisynth script looks like uncompressed video for application ... or, it has to be MPEG2? VLC can stream to network but I don't know if this can be used with MVP

EDIT: Becuse I'm playing mostly DivX/XviD files so leaving in MPEG2 doesn't work for me.

[Networker]

There are some plugins that use(d) the VLC app to stream from AVI to MPG2, the limitation, IIRC, is the MVP it can only handle MPEG2/3 decoding and I think MPEG1.. It does not handle AVI, it has to be transcoded from AVI to MPEG2 and then set (streamed) to the MVP for display.

J