Hi,
Dr. Werner Fink wrote:
> On Mon, Mar 14, 2005 at 06:01:02PM +0100, Roland Praml wrote:
>
>>>>I've figured out if I replay the file with vdr, the bso(replay) thread
>>>>doesn't start with newer recordings
>>>
>>>And you have choosen the AC3 audio track during replay the
>>>recording with the green button? I've this question because
>>>this is the first report of that kind.
>>
>>yes i've tested it several times.
>>I've tracked down the problem a little bit. Data is sent to the plugin
>>but the replay thread doesn't start because ScanPayOfPS1 fails.
>>
>>I've commented out these two lines:
>> case 0x0b:
>> // if ((uint_16)dvb != AC3magic)
>> // break;
>>and now it works.
>
> Hmmm ... this implies that the offset
>
> off_t o = (off_t) (ul & 0x0000ffff) + 3;
>
> is not correct because the stream is moved forward
>
> dvb += o;
>
> to the start of the magic word of the frame which should
> start there. As this works with stuff from DVD trailers
> I assume that something goes wrong elsewhere, e.g. in the
> cDolbyRepacker class.
>
> [seeking VDR sources]
>
> OK it _is_ a bug in the cDolbyRepacker class, therefore
> I've added Reinhard to CC.
>
> IMHO the declaration of AppendSubStreamID includes
> an error:
>
> void cDolbyRepacker::AppendSubStreamID(void)
> {
> if (subStreamId) {
> pesHeader[pesHeaderLen++] = subStreamId;
> pesHeader[pesHeaderLen++] = 0x00;
> pesHeader[pesHeaderLen++] = 0x00;
> pesHeader[pesHeaderLen++] = 0x00;
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> The minimal size is 0x01 and never 0x00
> }
> }
>
> ... OK, in the firmware I've included a workaround for
> such broken sub audio header. Nevertheless this should
> be corrected :^) ... Reinhard?
Looks like you got me, Werner ;-)
I've just had a closer look into xine's sources (demux_mpeg_block.c) and
it seems that my substream header is wrong most of the time.
Byte 0: substream id => correct
Byte 1: number of AC3 frames starting in this PES packet => wrong
Byte 2+3: offset to first AC3 frame relative to PES payload => wrong
As cDolbyRepacker assures that 1 frame is put into 1 PES packet, byte 1
should be 1 and byte 3 should be 4.
But what about extremely large AC3 frames, e. g. 1920 words = 3840
bytes. By assuring that PES packets don't get larger than 2048 bytes it
can happen that such a PES packet contains just the "middle" of an AC3
frame. How should bytes 1 to 3 be set in such a case?
Bye.
--
Dipl.-Inform. (FH) Reinhard Nissl
mailto:rnissl@xxxxxx
