how are hdtv sub-channels identified in TP files

[cat6man]

How does BTV4 identify which sub-channel or pid has been set for a recording? I know that the TP stream has all the sub-channels recorded and viewers like VLC and video-redo can select individual sub-channels to play and/or save.

Can someone tell me how BTV keeps track of which one to play? Is this information kept in the TP file somehow?

I'm asking because of issues playing back TP files on my network player. It always selects the x.1 subchannel to play, which is fine for all the OTA channels I get EXCEPT for local PBS which is on channel 13.3.......so I can't watch my recorded channel 13 pbs shows on my network player.

Someone on a separate forum (Zensonic z500) said that there is supposedly a problem with DVICO cards messing up a table somewhere in the transport stream that keeps track of things.....anyone familiar with this and does this have anything to do with keeping track of which sub-stream to play?

[KeeterJ]

I understand your problem. I have the same problem with transport stream files captured from my ATI HDTV card. So far, I have not found any commonly available software player (BTV, Windows Media Player, etc.) that lets you choose which stream to watch. Some seem to pick the highest subchannel and some pick the lowest. It's very annoying. It's also very weird to play the same file in different programs and get a completely different TV program from each one.

I have not researched it, but I suspect BTV4 is saving the desired subchannel number in an XML file somewhere on the local machine so it knows what to play later. In addition to your remote playback issue, there are two other problems with that. It means the files it saves are twice as big as they need to be since it saves both subchannels in the single stream file. On the other hand, if you want to record both subchannels simulaneously (a common thing on PBS for me), it won't let you specify both and play both, even though you are capturing the data for both in one combined .tp file.

It's obvious SnapStream needs to do more work with transport stream capturing/editing/storage. I'm hoping we see improvements in a future BTV 4.1 or 4.2.

In the mean time, I am using a program called HDTVtoMPEG2 to split the stream into the channels I want. I do NOT convert them to MPEG, and I do not edit them, I just create a separate .tp file for each subchannel. Then I can view either or I can discard the ones I don't want to keep. It's a nuisance, I know, but it works and is pretty fast. The program is at http://www.eecs.umich.edu/~balazer/H...EG2/index.html I set it up on my PC to launch it when I tell BTV4 to run the archive program. That saves me having to drill around for the program and the file name.

I hope this helps provide a temporary workaound for you until SS can give us more features to control this.

[nrf]

in btv4, you can change sub-channels during playback with the [ and ] keys.
VLC also lets you select the program.
nrf

[KeeterJ]

Originally Posted by nrf

in btv4, you can change sub-channels during playback with the [ and ] keys.
nrf

Wow! I tried it and it works! I'm wondering how you figured that out -- I just looked (again) I still don't see that info in the BTV4 keyboard help. Do you have any idea how to do that with a Firefly remote?

It works, and is a big help, but it still does not reflect the correct program information and channel number in the on-screen status info. Perhaps they could retrieve that from the PSIP info embedded in the transport stream, even if they did not capture the details from the net-based guide when the program was recorded.

Originally Posted by nrf

VLC also lets you select the program.
nrf

I just Googled VLC to see what you were referring to. I'll give it a try later today.

Thanks for the info.

[cat6man]

thanks....i was going to reply about vlc media player but you beat me to it.
i neve knew about the [ ] option...how did you find this?

also, video-redo will save whichever sub-program you want....nice package
and a free trial to see if you like it.

my understanding now is that there is a table/file in the TP stream that says what/where the sub-programs are within......

does BTV edit this stream' table to place the recorded sub-program in the 1st position so that it gets played by default?

[nrf]

actually, I only found out about the [ and ] keys when I put in a trouble report for a beta build. I've had some intermittent issues with the wrong one playing, or flipping to a wrong one when changing from windowed to full screen or the reverse.

I also use hdtv2mpeg do strip out other streams, but have had some issues with it, like 720p streams not playable, and short output files unusable.

evidently the streams contains lots of info, but btv must be saving information about the actual one you wanted to see in its own data.

[turls]

even in 4.1, switching between windowed and fullscreen breaks this. It should stay on the stream you've chosen until you exit, in fact it should remember it if you quit in the middle.

[nrf]

yes, I reported that.
nrf

[turls]

duh, yes you said that in the previous message if I would have read a little closer. At least I know I can get to it in Beyond TV so I'm better off than I was this morning.

[karhill]

Originally Posted by cat6man

How does BTV4 identify which sub-channel or pid has been set for a recording? I know that the TP stream has all the sub-channels recorded and viewers like VLC and video-redo can select individual sub-channels to play and/or save.

Can someone tell me how BTV keeps track of which one to play? Is this information kept in the TP file somehow?

Yes, this would be good to know. BTV has to expose this information somehow, so 3rd party add-ons know which sub-channel was requested by the user and can operate on the appropriate sub-channel.

[nrf]

btv barely seems to be able to keep hold of it, though. just resizing the window makes it rotate one to the right. I then have to hit [ to get back where I was.