Where can I read about graphs and codecs?

[pvr_noob]

Hi,

I've recently set up a media centre PC and am really happy with gbpvr. I have a few questions, but the most pressing one is: Where can I read about graphs and codecs? It seems like there are many solutions available when it comes to codecs (SAF, K-lite etc) but I don't entirely understand the reasoning behind those packages, or how they really work. I also have no idea what a graph is, and how to use it to my advantage. I would like to understand those things so I can fiddle with my media centre without sending it to "codec hell".

It seems like the concept of graphs are thrown around a lot, but aside from the DirectShow wikipedia entry, I don't really know anything about them.

[spotty]

Hi,
I've asked this question too without getting much of an answer.
I can give you some disjointed points that I have discovered along the way-
-Programs that use graphs get directshow to construct the graph (which is essentially a set of codecs etc (called 'Filters') connected together) required to display or convert video.
- The programs (eg GBPVR) can try to get directshow to use certain codecs (filters) etc (but it may not work if directshow cannot find compatible inputs/outputs to connect together)
- when directshow is picking the codecs (filters) to use, it uses a merit system. You can change the value of merit each codec (filter) etc has in the registry (CAUTION). Directshow also gives bias to filters that have worked correctly in a situation before.
- Installing codec packs _can_ substantially change codec/filters merits causing some types of files to playback well, others to not work at all. Once you try to fix this situation you soon realize where the term 'Codec Hell' comes from.
- to see a graph, there is a setting, I think in GBPVR config, to 'allow external graph connection' or something like that (1) turn this on, (2) start video playing in GBPVR (3) then use-
"http://blog.monogram.sk/janos/tools/mono...aphstudio/" (better than graphedit) to 'connect to remote graph'. You will see the filters as rectangular blocks and wires connecting them together. You can pause the graph, insert more filters and re-connect them to experiment with what works. That will tell you what can work. Use these codecs in GBPVR config. Start playback again. Check if the graph created is what you want - if it isn't you may need to change merits but thats where I stop because changing merits can easily get you into Codec Hell.

Hope that helps.

NB I have _heard_ that k-lite or community codec packs are reliable these days - perhaps my fears of codec packs wrecking the merits are out of date but I can't confirm this - Could someone who really knows please comment?

[Graham]

GBPVR will create .grf files if you edit config.xml to include ...

<SaveGraphFiles>true</SaveGraphFiles>

These files can be opened with graphedit or graphstudio. They clearly show the sequence of filters used by GBPVR.

You could start PVRX2 and watch a recording then stop PVRX2 and open the .grf file to see the filters used. You could then start PVRX2 and view the same file using Video Library (which uses a different mechanism to choose filters). You might see different filters in the two .grfs. This is not necessarily a bad thing but it gives an insight into what is going on under the covers.

My own opinion, find the smallest possible number of decoders that will play all of your stuff. Uninstall all of the others.

[whurlston]

Hi,

I've recently set up a media centre PC and am really happy with gbpvr. I have a few questions, but the most pressing one is: Where can I read about graphs and codecs? It seems like there are many solutions available when it comes to codecs (SAF, K-lite etc) but I don't entirely understand the reasoning behind those packages, or how they really work. I also have no idea what a graph is, and how to use it to my advantage. I would like to understand those things so I can fiddle with my media centre without sending it to "codec hell".

It seems like the concept of graphs are thrown around a lot, but aside from the DirectShow wikipedia entry, I don't really know anything about them.

http://wiki.jrmediacenter.com/index.php/...back_Guide is probably the best documentation I've ever seen.