OGM = AVI In OGG ?

[ChristianHJW]

I was stressing my brains like crazy when i heard that you guys can transmux AVI files containing DivX/XviD with AC3 audio into OGM, thinking '... hell, how has Tobias done this ..' . There was a chance he could demux the VfW video streams from AVI and put this into Ogg somehow, but how could he handle AC3 this way ?

Now recently Suiryc and robux4 had a nice converation about the way OGM is supported in VirtualDubMod and how he can seek to keyframes etc. ( big probs in Ogg for the time being ), and it became obvious that Tobias has put the complete AVI container into the Ogg container ??

Anybody here can confirm ? Suiryc ?

[Koepi]

Nope, I don't think it's that easy.
He somewhre wrote that he demuxes the avi into the raw videostream and packs it up into ogg frames/pakets. Same is valid for sound.
If he'd just put the whole avi container into OGM the final OGM would be quite huge, I think. But let's stress the search button %)

Regards
Koepi

[Suiryc]

Originally posted by ChristianHJW
Now recently Suiryc and robux4 had a nice converation about the way OGM is supported in VirtualDubMod and how he can seek to keyframes etc. ( big probs in Ogg for the time being ), and it became obvious that Tobias has put the complete AVI container into the Ogg container ??

Anybody here can confirm ? Suiryc ?
You misunderstood a bit what we said here. The way data are muxed in OGM is : the muxer receives a frame (video or audio) with some information about it (size, is it a keyframe ? how many samples in it, ...), put it in a Packet (the Packet header - 1-9 bytes long - contains the info about the data), give it to the Ogg library and voila :)

Now what I do for seeking is : I parse the entire file, store info about all the data (where are the frames, are those frames keyframes, ..., - like does VDub with AVI container : it also store in memory info about the frames). Then when VDub need a frame, I have enough info to go and get it as fast as possible :)
Maybe you misunderstood the "like does VDub for AVI container" :(

[BlackSun]

Originally posted by Suiryc
Now what I do for seeking is : I parse the entire file, store info about all the data (where are the frames, are those frames keyframes, ..., - like does VDub with AVI container : it also store in memory info about the frames). Then when VDub need a frame, I have enough info to go and get it as fast as possible :)
Maybe you misunderstood the "like does VDub for AVI container" :(

But isn't Vdub doing that only if the frame index is missing (since it's at the end, it's often missing) ? Actually for OGM/MPEG/MCF you parse the entire file because there is no index, you don't need that with AVI (exept in the case I mentionned)

[neo_sapien]

Originally posted by ChristianHJW There was a chance he could demux the VfW video streams from AVI and put this into Ogg somehow, but how could he handle AC3 this way ?

It seems to me that so far, no program can handle AC3 that way, correctly that is, without transmuxing the AVI+AC3 the way that Oggmux does. If you try to mux AVI+AC3 into an OGG container using Suiryc's programs, you get okay playback so long as the audio decoder DSF isn't set to SPDIF. 2 channel downmixing in the audio decoder DSF seems to produce an actual audio stream, but in SPDIF you just get static. Somehow, however, if you cut an Oggmux'ed file with ogmcutter, it still works fine.

Now, other users may have experiences different from my own in this matter, but IMO, the only thing that works 100% for AVI+AC3 in OGG is OggMux.

[Suiryc]

Originally posted by BlackSun
But isn't Vdub doing that only if the frame index is missing (since it's at the end, it's often missing) ? Actually for OGM/MPEG/MCF you parse the entire file because there is no index, you don't need that with AVI (exept in the case I mentionned)
Yes, but it still keep in mind information about the frames (if the index is there, then all needed information are in it, otherwise it parse the whole file).

[Suiryc]

Originally posted by ChristianHJW
There was a chance he could demux the VfW video streams from AVI and put this into Ogg somehow, but how could he handle AC3 this way ?
Oops I missed this one.

The job is made by DirectShow. Since OggDS is a DirectShow filter, it treats data coming from its input streams.
As the AVI containing Video+Audio is demuxed by a DShow filter and that data are then served to next filters (Ogg Muxer filter in this case), it is not a problem : the Ogg Muxer filter receives video and audio data (with all necessary information about those data) thanks to DirectShow.