Re: [xine-devel] FIX: libmpeg2 sets wrong (mpeg1) aspect ratio for mpeg2 streams

[Thibaut <tma...@no...>]

i'm resending this message, my ISP seems to be blacklisted

Hi Reinhard,

----Message d'origine----
>De: Reinhard Nissl <rnissl=40gmx.de>
>A: xine-devel=40lists.sourceforge.net
>Copie =E0: mroi=40users.sourceforge.net
>Sujet: =5Bxine-devel=5D FIX: libmpeg2 sets wrong (mpeg1) aspect ratio for=
 mpeg2 streams
>Date: Wed, 15 Sep 2004 00:56:19 +0200
>
>Hi,
>
>the attached patch fixes the following problem: when libmpeg2 sets the as=
pect =

>ratio of the stream it doesn't know whether the stream is mpeg1 or mpeg2 =
and =

>therefore chooses mpeg1. The missing information about having a mpeg2 str=
eam =

>is available a little bit later but it's to late for setting the apect at=
 that =

>time again.

Right, this is a bug.
When a sequence header (0xb3) is parsed, picture->mpeg1 is set to 1, then =
if a header extension (0xb5) is parsed picture->mpeg1 is set to 0, it's ho=
w a mpeg2 stream is detected. When a picture start code comes, you know if=
 it's a mpeg1 or mpeg2 frame.

There is a problem because a frame format event is sent when a sequence he=
ader is parsed, and at this time you don't know if it's mpeg1 or mpeg2 seq=
uence and the default value is used.

Your patch uses the type (mpeg1/mpeg2) of the previous sequence, i agree t=
hat it should work, but i consider this as a hack.
I think the event should be sent at the first picture start code of the se=
quence, it's easy to detect the first picture, and at this time you know i=
f it's mpeg1 or mpeg2.

Question for engine guys, why is this event sent by decoders ?
The information is not in sync with the output, and we have to duplicate t=
his code to other decoders. IMHO it would be better to do this kind of stu=
ff in the output loop.

>The patch now assumes an mpeg2 stream by default and falls back to mpeg1 =
if it =

>doesn't see an mpeg2 packet between two aspect ratio packets.
>
>I've tested it with mpeg1 and mpeg2 streams and it seems to work.
>
>Bye.
>-- =

>Dipl.-Inform. (FH) Reinhard Nissl
>mailto:rnissl=40gmx.de

Thibaut