[MPlayer-users] Reencoding a broadcast HD-ATSC stream

[Norman Ramsey]

 > On Thu, 17 Nov 2005 21:08:51 -0600
 > Kichigai Mentat <kichigai at comcast.net> wrote:
 > 
 > > High bitrate (approximately half of the MPEG-2 TS, I'd say, about 1.5 
 > > MBit, but many people use around 700-800 Kbits, 
 > 
 > If you're encoding a 1920x1080 video with a bitrate of 700k, it will
 > certainly be unwatchable.  Even 1500 is optimistic.

I'll second that, although I'm encoding sports, which has a lot of
motion.  (Pause to curse broadcasters who give us sports in 1080i
instead of 720p.)

With help from man pages and suggestions in mplayer-doc, I've been
working on a script to encode HD-ATSC broadcasts for archiving onto
DVD.  I'm using libavcodec (-ovc lavc) and have tried both the mpeg4
('divx') and mpeg2 video codecs.  Targeting a 3-hour game to either 1
or 2 dvds, this means vbr in the area of 2000-4000 kb/sec (if I
remember correctly).  From my experiments, I have learned the
following:

  1. I haven't been able to get any results I like using the mpeg4
     codec at the native resolution.  Blocks, artifacts, you name it;
     the video doesn't look good.  Plus my poor CPU just about rolls
     over and dies trying to play the stuff.

  2. If I scale to NTSC DVD resolution (720x480), the results from
     mpeg2 coding look quite good, particularly at the higher of the
     two bit rates, at least if my initial content is 720p.
     Deinterlacing the 1080i seems to make everything blurry; I am
     still experimenting in that arena.

  3. I am having *terrible* problems copying the AC3 audio (as RC
     suggests).  Details in a separate post, but I get error messages
     from mencoder, warnings from dvdauthor, and when I put the dvd
     itself into a hardware player, it is 'mostly frozen' with short
     snatches of motion/audio.  I suspect the problem is bad
     Presentation Time Stamp somewhere, but it beats me how to
     diagnose it, let alone cure it.


Norman