Understanding Playback

[dennit]

Here's a quote from sub:

GB-PVR does not do any of the playback of .mp3 files itself. It just relies on the machine Directshow filters to play them. If you run GraphEdit and can select the 'render media file' menu option, then select your file, and it works then it should also work in GB-PVR.

This quote and similar ones helped me solve my .mp3 playback issue by using GraphEdit. Armed with this knowledge, I confidently tried to solve my current .mkv playback issue. I'm getting no sound when playing through the video library.

I dropped the mkv file into GraphEdit and it played with video and sound. My initial reaction was that if it played in GraphEdit, it should be playing in GB-PVR. For some reason, I thought I had read that the various playback rendering settings in config applied only to GB-PVR recordings and not to files like this .mkv file. I thought, like the .mp3 case it was just handed off to the DirectShow filters to be played.

A little poking into the logs and swapping rendering settings in config convinced me that this was not correct. I managed to lose video too, by changing config and I see the filters listed from config trying to be used to playback the .mkv file. Now the odd thing is that when I try to use the filters that I think are being used by GB-PVR to play back in GraphEdit, it works in GraphEdit and when I try to choose filters in config that worked in GraphEdit, it still doesn't work in GB-PVR.

Perhaps I've made a mistake. I'm not certain that I've got the right decoders and renderers matched up, but I think I did. Regardless, what I'm really looking for is understanding so I can troubleshoot myself. I think I'm missing something about how video is played, what filters are selected by GB-PVR, how config controls the selection, what part filter merit plays in this and how GB-PVR's playback differs from what I see in GraphEdit.

IOW, I want to be able to help others and not bother sub and post logs every time I've got some minor playback issue of my own. Is there a Wiki entry about troubleshooting or a post that might help me figure some of this out? Thanks in advance.

[sub]

The file types that get recorded by GB-PVR (.ts .mpg) get a little bit of special treatment, but when it comes to files like .mkv or .mp3 then its pretty much all left up to directshow.

The only exception is the audio render and video renderer. For example, to emulate what GB-PVR does when playing a .mp3 file - if the config app app has the audio renderer set to anything other than 'system default', then start graphedit and select the 'insert filter' menu option and add the audio renderer you selected, then hit the 'render media file' option. This should give you the same graph as you'd get in GB-PVR.

For audio files this only applies to the 'audio renderer' filter, which could be added prior to the render. For misc video files, like .mkv, the filters that may be added prior to rendering are the audio and video renderers (if set to something other than 'system default'). You can see the list of directshow filters that ended up getting used by looking in pvrx2.exe-native.log after attempting to play your file.

All the filtermerit stuff is handled by directshow and no different in GB-PVR.

One think to be aware of though is the ffdshow filters are a bit of a special case which can cause a difference between graphedit and other apps like GB-PVR. The ffdshow filter contains configuration options which tell it which applications it can be used in, and it has WMP and GraphEdit preconfigured in that list, but not GB-PVR. This can cause video or audio to be available in GraphEdit, but no suitable decoder to be found when playing from a less common Directshow app like GB-PVR. In this specific case you can go into the ffdshow configuration and add the PVRX2.exe executable to the list of enabled apps.

[dennit]

The file types that get recorded by GB-PVR (.ts .mpg) get a little bit of special treatment, but when it comes to files like .mkv or .mp3 then its pretty much all left up to directshow.

The only exception is the audio render and video renderer. For example, to emulate what GB-PVR does when playing a .mp3 file - if the config app app has the audio renderer set to anything other than 'system default', then start graphedit and select the 'insert filter' menu option and add the audio renderer you selected, then hit the 'render media file' option. This should give you the same graph as you'd get in GB-PVR.

For audio files this only applies to the 'audio renderer' filter, which could be added prior to the render. For misc video files, like .mkv, the filters that may be added prior to rendering are the audio and video renderers (if set to something other than 'system default'). You can see the list of directshow filters that ended up getting used by looking in pvrx2.exe-native.log after attempting to play your file.

All the filtermerit stuff is handled by directshow and no different in GB-PVR.

One think to be aware of though is the ffdshow filters are a bit of a special case which can cause a difference between graphedit and other apps like GB-PVR. The ffdshow filter contains configuration options which tell it which applications it can be used in, and it has WMP and GraphEdit preconfigured in that list, but not GB-PVR. This can cause video or audio to be available in GraphEdit, but no suitable decoder to be found when playing from a less common Directshow app like GB-PVR. In this specific case you can go into the ffdshow configuration and add the PVRX2.exe executable to the list of enabled apps.

Wow - that's 100% exactly the info I needed/wanted. The ffdshow info in particular probably explains some/most of what I was seeing as it was being used in GraphEdit. I was confused when the logs showing filters used by GB-PVR didn't seem to match up, even though I was using the same renderer. (I don't know how you hit this answer so perfectly when I didn't even mention ffdshow.)

One last question/confirmation. I've been using GraphEdit by simply selecting a file to render from GraphEdit's menu. If I read the above correctly, then you're saying by doing that I was using the system default renderer, but I could force GraphEdit to render using something other than the default by putting that renderer onto the GraphEdit screen before selecting the file to render? And by selecting the same renderer defined in config I should get GraphEdit to do what GB-PVR does. That's great.

I've been reading miscellaneous threads just to pick up details like this, but I wish there was a thread containing the real cream of the crop posts like this one. Thanks!

[sub]

Wow - that's 100% exactly the info I needed/wanted. The ffdshow info in particular probably explains some/most of what I was seeing as it was being used in GraphEdit. I was confused when the logs showing filters used by GB-PVR didn't seem to match up, even though I was using the same renderer. (I don't know how you hit this answer so perfectly when I didn't even mention ffdshow.)

No worries.

One last question/confirmation. I've been using GraphEdit by simply selecting a file to render from GraphEdit's menu. If I read the above correctly, then you're saying by doing that I was using the system default renderer, but I could force GraphEdit to render using something other than the default by putting that renderer onto the GraphEdit screen before selecting the file to render? And by selecting the same renderer defined in config I should get GraphEdit to do what GB-PVR does. That's great.

Correct.

[dennit]

No worries.

Just to close this thread out - Thanks, the .mkv problem is sorted.