On Mon, Jun 18, 2012 at 10:21 AM, Dieter BSD <dieter...@engineer.com> wrote: > user.vdr writes: >> Recording doesn't require any compression unless you are transcoding >> in real-time. There's no difference between recording ATSC, NTSC, PAL, >> etc, and it's actually irrelevant what the stream is. > > This is incorrect. ATSC is compressed before broadcast, so > you receive the data already compresed. NTSC and PAL are > broadcast in analog. The tuner performs A-to-D which gives > an uncompressed data stream. Have fun trying to store that. > As a practical matter, you have to compress the data in real time. > Some, not all, tuners include hardware compression.
All consumer digital broadcasts are compressed typically with mpeg2 or mpeg4. With very very very few exceptions, all analog NTSC broadcasts have been switched to digital, by the FCC mandated deadline of June 12, 2009. Tuners perform demodulation, not decompression. There are a few "premium" or "full-featured" devices which have an on-board decoder such as a Hauppauge Nexus-s or the TechnoTrend S2-6400. You absolutely do NOT have to reencode a stream unless you want to alter the resolution, bitrate, or compression method. Tuners do NOT provide raw audio/video to the system in any case. >> Lastly, it's possible to save a single channel or the entire stream >> which usually contains several channels. Even when saving the full >> stream, it likely uses far less bandwidth than your media offers so >> there's no problem there. > > This appariently refers to ATSC. Yes, modern disks have plenty > of bandwidth to store the entire ATSC stream. The main reason > to filter PIDs is to save disk *space*. Also, some software > can't select which program to decode. It refers to ANY multiplex. Again, the standard used for broadcast is irrelevant. Also, any program that can tune a channel has the ability to filter the pids, otherwise it would be impossible to tune a channel. > Wojciech writes: >> most people vastly underestimate power of modern CPUs. > > Many people overestimate the "moderness" of most people's CPUs. An old Pentium 4 3ghz can decode HD with plenty of cpu resources to spare so unless a person using something older than that, they've certainly got "modern" cpu power. _______________________________________________ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "freebsd-hackers-unsubscr...@freebsd.org"
