[FFmpeg-devel] [RFC] use ff_avc_find_startcode in ff_find_start_code

[Måns Rullgård]

Reimar D?ffinger wrote:
> Hello,
> On Tue, Feb 19, 2008 at 03:20:07PM -0000, M?ns Rullg?rd wrote:
>> Reimar D?ffinger wrote:
>> > On Tue, Feb 19, 2008 at 03:06:37PM -0000, M?ns Rullg?rd wrote:
>> >> Reimar D?ffinger wrote:
>> >> > On Tue, Feb 19, 2008 at 03:28:27PM +0100, Reimar D?ffinger wrote:
>> >> >> For decoding my THX_Science_FLT_1920.gxf, ff_find_start_code in
>> >> >> mpeg_decode_frame
>> >> >> is called 73754 times for 353 frames, the average amount of data skipped
>> is
>> >> >> 1272.626343 bytes.
>> >> >
>> >> > And uh... yes, this does indeed mean that 90% of the file's data is
>> >> > trash...
>> >> > Probably there is not much point in concentrating on this kind of thing,
>> >> > but I'd expect these kind of long skips might be common for DVDs in
>> >> > order to try to get a more constant bitrate as well...
>> >>
>> >> DVDs generally use the standard MPEG2-PS padding stream, so this should
>> >> not be an issue there.
>> >
>> > I checked that btw., with DVDs there usually (more than 50% of cases) is
>> > a 5 byte skip and then the start code.
>> > But the Spaceballs DVD has an skip of 140 byte on average in the first
>> > 10 minutes, going down to an average of 70 later on.
>>
>> Where are these skips?
>
> As said above, by ff_find_start_code in mpeg_decode_frame, i.e. at least
> before every slice start.

So you're saying there are stuffing bytes between slices in the MPEG2
elementary stream?

-- 
M?ns Rullg?rd
mans at mansr.com