Re: [Libquicktime-devel] FFmpeg plugin resync DNW for out-of-order B-frames after full sync keyframes

[Derek C. <der...@mi...>]

Apologies, the problem still happens with my latest
resync_bframes_after_full_sync_frames3.patch - I want to change the
line:

int skip_initial_bframes = sync_disp_frame <= target_display_frame;

to

int skip_initial_bframes = sync_disp_frame < target_display_frame;

but will need to investigate a suspicious side-effect I'm having with
my test file...


On 24 April 2014 10:57, Derek Chow <der...@mi...> wrote:
> I've revised and tidied up the initial patch to fix bad logic where it
> only skips one B-frame when it should be able to skip more than one
> until the next non-B-frame.
>
> I think this thread got lost amidst Burkhard's packet index work but
> it is still a valid problem regardless of how we 'retrieve the
> previous ref sample', 'check the PTS of a sample', 'check if sample is
> B-frame'.  Basically, if you have a packet sequence like:
>
>        pos 1155584 pts 0 dts 0 dur 100 sz 56956 FT I key ref
>        pos 1212540 pts -200 dts 100 dur 100 sz 1095 FT B
>        pos 1213635 pts -100 dts 200 dur 100 sz 35253 FT B
>
> and try to resync to the 3rd frame (PTS -100), the next frame to be
> decoded will end up being the 2nd frame (PTS -200).
>
> Once we are happy with the packet index generation, we can go ahead
> with simplifying the *bitstream*() function code to use it.  -- Side
> note, I've just come across a file that generates "? key" packet index
> entries so for now I've had to use the current demux code - I'll debug
> and update on the "New Demultiplexing mode" thread later.
>
> On 5 March 2014 09:38, Derek Chow <der...@mi...> wrote:
>> (sorry I've switch email client and forgot to send as plain text -
>> original message below):
>>
>> Example with XDCAM file:
>>
>> (IBBP... bitstream with 'ctts' 2, -1, -1, 2 ...).
>> After seeking (or decoding) to frame 2, use
>> quicktime_set_video_position() to then seek backwards to frame 1.
>> get_bitstream_sync_frame() returns 0.
>> decoded_frames_to_discard becomes < 0 despite "// Should not be < 0
>> unless the stream is broken."
>>
>> Please see possible fix attached.
>>
>> On 4 March 2014 10:10, Derek Chow <der...@mi...> wrote:
>>> Example with XDCAM file:
>>>
>>> (IBBP... bitstream with 'ctts' 2, -1, -1, 2 ...).
>>> After seeking (or decoding) to frame 2, use quicktime_set_video_position()
>>> to then seek backwards to frame 1.
>>> get_bitstream_sync_frame() returns 0.
>>> decoded_frames_to_discard becomes < 0 despite "// Should not be < 0 unless
>>> the stream is broken."
>>>
>>> Please see possible fix attached.
>>>
>>>
>>> Derek Chow / C++ Developer
>>>
>>> der...@mi... / +44(0)7825373230
>>>
>>> Office +44 (0)207 884 2530
>>> 21 Broadwall, London, SE1 9PL, United Kingdom
>>> http://www.mirriad.com
>>
>>
>>
>> --
>>
>>
>> Derek Chow / C++ Developer
>>
>> der...@mi... / +44(0)7825373230
>>
>> Office +44 (0)207 884 2530
>> 21 Broadwall, London, SE1 9PL, United Kingdom
>> http://www.mirriad.com
>
>
>
> --
>
>
> Derek Chow / C++ Developer
>
> der...@mi... / +44(0)7825373230
>
> Office +44 (0)207 884 2530
> 21 Broadwall, London, SE1 9PL, United Kingdom
> http://www.mirriad.com



-- 


Derek Chow / C++ Developer

der...@mi... / +44(0)7825373230

Office +44 (0)207 884 2530
21 Broadwall, London, SE1 9PL, United Kingdom
http://www.mirriad.com