[ATrpms-users] dvdauthor error

[Axel Thimm]

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.

> 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
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