[mythtv-users] wrong bitrate detected

[Dawning Sky]

On 3/10/06, Marco Nelissen <marcone at xs4all.nl> wrote:
>
> >Hi,
> >
> >I have some low bitrate recording from my local PBS station (KQED San
> >Francisco) in digital SD that I recorded off the Comcast cable using
> >HD-3000.  Half an hour worth of recording is about 800MB.  So I
> calculated
> >the bitrate is about 1800 kbps.
>
> If a half hour is 800 megabytes, then wouldn't that be 800*1024*8 kilobits
> for 1800 seconds, or 3640 kilobits per second?


:)  Hadn't had my first cup of coffee when I posted this.  You're right.  It
should be about 3600 kbps.


>  MythTV is having problems playing back
> >these recordings.  It plays as if it's in slow motion.  And the sound is
> >distorted too--shifted to lower frequency.  And in the frontend log I
> found
> >out that MythTV thought the recording was at 81 kbps.
> >
> >   stream: start_time: 8234.631 duration: 82875.702 bitrate=81 kb/s
>
> I wouldn't be surprised if kb/s actually meant kilobytes per second. Not
> everyone is equally consistent with the use of 'k' vs 'K', 'b' vs 'B',
> etc.



I think MythTV does report bits per second.  On other recordings it would
report something like 17960 kb/s.  As for whether it means kilo/kibi (k/Ki),
I have no idea.  But for our discussion, kilo and kibi are sufficiently
close to each other.

It would be interesting to chop a few minutes off the start of the file
> and try to play the remainder and see what it says about the bitrate then.
> Most bitrate detection problems I've come across are with variable-bitrate
> streams where the application only looks at the first few frames to detect
> bitrate.


I would try your suggestion.  But who should I blame for this, the
broadcaster or the application, if this is indeed the problem. :)

Marco
>

DS
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