[ATrpms-users] dvdauthor error

[Jeffrey J. Kosowsky]

Axel Thimm wrote at about 22:26:41 +0200 on Tuesday, January 15, 2008:
 > On Tue, Jan 15, 2008 at 01:01:51PM -0500, Jeffrey J. Kosowsky wrote:
 > > Axel Thimm wrote at about 18:43:30 +0200 on Tuesday, January 15, 2008:
 > >  > On Thu, Jan 10, 2008 at 09:01:50AM -0500, Jeffrey J. Kosowsky wrote:
 > >  > > Now, according to the log file (see above), the xml file seemed to
 > >  > > specify a bitrate of "15000000" (or 15mb/sec),
 > 
 > I looked this up and 15 MB/sec is the mpeg2 default for
 > 720x576 at 30Hz. So maybe this is what the xml file maps to?
 > 
 > OTOH DVD bitrates define a max peak at about 10MB/sec (e.g. in this
 > sense DVD is not really a full mpeg2 implementation), while DVB allows
 > the full 720x576 at 30Hz bitrate.
 > 
 > E.g. I think you will always need to transcode a full (SDTV) DVB
 > stream to allow recording on DVD.
 > 
 > >  > > which would exceed the 1080kb/sec limit. On the other hand
 > >  > > since the actual recording was 2 hours long and the total
 > >  > > length was 2.85GB, the (average) bitrate was more like
 > >  > > 3.1kb/sec (2850000*8/3600/2). So, unless the bitrate is highly
 > >  > > variable (this is an atsc dvb recording), it probably did not
 > >  > > exceed the limit too much.
 > >  > 
 > >  > I think you missed a couple of zeros in the GB :)
 > >  > 
 > >  > E.g. it's more like 2.85 * 1024^3 Bytes (kilo -> mega -> giga).
 > >  > 
 > >  > > So, I'm not really sure what is going on here unless it really is a
 > >  > > bitrate issue with the variable bitrate truly exceeding the dvd max
 > >  > > too often.
 > >  > > 
 > >  > > Any thoughts/advice here...
 > >  > 
 > >  > Does the missing "1000" fix this? At least is seems to bring the
 > >  > numbers in the same order.
 > >  > -- 
 > > 
 > > You are right - I did the conversion to kilobytes twice :)
 > > i.e. the answer is: 2850000*8/3600/2 kb/sec = 3166 kb/sec = 3.2mb/sec
 > > 
 > > However, 3.2 mb/sec = 0.4 mB/sec which should not be exceeding the
 > > dvd rate -- an easy way to see this is that a full 2 hours of
 > > recording fit in 2.85GB of space and we all know that a regular 2 hour
 > > mpeg2 commercial DVD movie takes up more than that...
 > 
 > 3 Mbit/sec sounds more like 352 × 288/240 resolution. Was that the
 > resolution of the captured file? In that case the DVB and DVD
 > standards of mpeg2 overlap, but then you need to make TS to PS, so I
 > think at the end you will always have to transcode DVB->DVD formats.

I'm not sure what the original resolution was and I have since
transcoded it. But, I just looked at another recording that according
to mplayer is:
  VIDEO:  MPEG2  704x480  (aspect 2)  29.970 fps  15000.0 kbps (1875.0 kbyte/s)

However, the 1/2 hour recording is exactly 995413188 bytes, which
corresponds to: 995413188/1800 = 553007 bytes/s = 553 kbyte/s = 4424
kbps.

This again seems close to the "Low Level - 352x288" flavor of mpeg-2
but I am confused to why mplayer calls it 702x480 and 15000 kbps...


 > > So, while my math was sloppy :), the problem remains unsolved for me
 > > again unless there is huge variability in the bitrate which results in
 > > transitory speeds much higher than 0.4 megabyte/sec. (or so it seems
 > > to me :)
 > 
 > Maybe it isn't a bitrate but a format problem then?
 > -- 
 > Axel.Thimm at ATrpms.net
 > 
 > [GNUPG:] ERRSIG 401552D4639A99F1 17 2 01 1200428801 9
 > [GNUPG:] NO_PUBKEY 401552D4639A99F1