Hi, On Mon, Jul 10, 2006 at 02:55:29AM -0700, Trent Piepho wrote: > On Sun, 9 Jul 2006, christophpfister@xxxxxxxxxxx wrote: > > It seems that the time has come to develop a new channel format for > > dvb-apps. Andrew and I agreed on the following style, but comments / > > suggestions / opinions are always welcome ;) > > There should be a parameter for the PID of the PMT. Even if you know the > PIDs of the audio and video streams, there is still information in the PMT > that is useful. I would never ever rely on PIDs in DVB if there is no strong reason to do so. You have the service_id, which is the key (together with ts_id and on_id) to the program; you can get all the information about the program from the data stream once you know these parameters. Specifying which audio stream to use is somewhat more difficult. For a full-featured application, just having a fixed PID is IMHO not the best choice. (E.g. there is something called "Hörfilm" at least in german-speaking part of europe, which adds another audio stream which, however, is silent most of the time. I would have to dig a bit deeper to look how yo can tell if the stream is active or not.) > For example, without the PMT mplayer will try to auto-detect the format of > the audio stream. This causes frequent audio skips on some stations. This > has a lot to do with the stupidness of mplayer TS demuxer, and I've fixed > my mplayer to virtually eliminate this problem. But it's still true that > there is information like language descriptors, conditional access > descriptors, stream format, etc. in the PMT that is part of the channel. exactly, and this is the reason why we should stick to service_id and let the application handle the rest by itself, parsing the tables it needs. > It is very common for channels to have multiple audio streams. I don't see > anything about how this is handled. Multiple audio_pid lines? Multiple > pids listed on one audio_pid line? Is there any way to associate a > language with an audio pid? Which audio pid should be the default? The > first one? See above. Dynamic switching might be necessary for a really cool application... The audio streams are normally associated to names (3-letter) that let you guess either the language or the use (e.g. "AC3", "2Ch" for "Hörfilm"), but you can not rely on the broadcasters to use any common scheme here. > Can PIDs be specified in hex? It seems like all the tools that print PIDs > print them in hex. It is quite common, in case we really want PIDs in the file, why not give both possibilities, simply to be distinguished by "0x" at the beginning? > Modulation should be mandatory for ATSC. > > Can a channel have multiple names? I'd like to be able to refer to > channels both by their number and the broadcaster's name. Regards, Wolfgang _______________________________________________ linux-dvb@xxxxxxxxxxx http://www.linuxtv.org/cgi-bin/mailman/listinfo/linux-dvb
