[Ffmpeg-devel] Interlaced decoding internals?

[Baptiste Coudurier]

Hi

Michael Niedermayer wrote:
> Hi
> 
> On Tue, Feb 27, 2007 at 11:45:08AM +0100, Baptiste Coudurier wrote:
>> Hi
>>
>> Baptiste Coudurier wrote:
>>> Hi
>>>
>>> Michael Niedermayer wrote:
>>>> Hi
>>>>
>>>> On Sun, Feb 11, 2007 at 01:58:12PM +0100, Baptiste Coudurier wrote:
>>>>> Baptiste Coudurier wrote:
>>>>>> Michael Niedermayer wrote:
>>>>>>> Hi
>>>>>>>
>>>>>>> On Tue, Feb 06, 2007 at 01:31:04PM +0100, Baptiste Coudurier wrote:
>>>>>>>> Michael Niedermayer wrote:
>>>>>>>>> On Tue, Feb 06, 2007 at 11:08:20AM +0100, Baptiste Coudurier wrote:
>>>>>>>>>> Hi
>>>>>>>>>>
>>>>>>>>>> Michael Niedermayer wrote:
>>>>>>>>>>> Hi
>>>>>>>>>>>
>>>>>>>>>>> On Mon, Feb 05, 2007 at 08:31:41PM +0200, Kostya wrote:
>>>>>>>>>>>> I'm working on adding interlaced frame support for VC-1 and
>>>>>>>>>>>> has some question regarding AVCodecContext internals:
>>>>>>>>>>>> What do avctx->interlaced_frame, avctx->top_field_first
>>>>>>>>>>>> and avctx->repeat_pict affect if set by decoder?
>>>>>>>>>>> they are not in AVCodecContext but AVFrame
>>>>>>>>>>> they affect display, top_field_first affects the order in which
>>>>>>>>>>> fields are shown, interlaced_frame affects if the frame is shown
>>>>>>>>>>> as frame or as 2 fields at 2 seperate times (assuming the player
>>>>>>>>>>> applictaion cares about the at all of course ...)
>>>>>>>>>> You'll laugh, what can I do if the interlaced info is in the container ?
>>>>>>>>>> I have some mjpeg a bottom field first, and info is in "fiel" atom.
>>>>>>>>>> I'll fix decoder, but I need a way to supply that info.
>>>>>>>>>> What do you prefer ? Adding a field to avctx ? 
>>>>>>>>> avctx is problematic as top-field-first can change between frames in
>>>>>>>>> MPEG so with decoder delay and multiple threads its the perfect recipe
>>>>>>>>> for troubble
>>>>>>>>> adding top-field-first to AVStream seems like the better solution,
>>>>>>>>> that way the demuxer can export it without interfering with the codec
>>>>>>>>> the same may (or may not ...) be a good idea for width/height, so
>>>>>>>>> the width and height for mpeg4/h263 in mov could be dealt with nicer
>>>>>>>>> maybe ...
>>>>>>>> So, then I need to set picture->top_field_first before passing it to the
>>>>>>>> decoder.
>>>>>>>>
>>>>>>>> Attached patch is working, but IMHO is ugly.
>>>>>>> yes this doesnt look good, i thought the container top field first was
>>>>>>> just for display if its needed for decoding then it must be passed through
>>>>>>> extradata that of course assumes that there is not enough information in
>>>>>>> the jpeg stream itself to decode it correctly (which i have some doubt about
>>>>>>> also we could choose simply not to support these jpegs)
>>>>>> I need to reread specs, AFAIK jpeg does not support interlacing,
>>>>>> mjpeg in mov/avi, specify total width/height in container, and field
>>>>>> height in bitstream.
>>>>>>
>>>>>> I would like to support them, bottom field is almost everytime used in NTSC.
>>>>>>
>>>>>>> also the changes to mjpeg.c contain cosmetics and ive a bad feeling about
>>>>>>> them (they arent breaking all interlaced non mov mjpeg or?)
>>>>>> Currently interlacing is detected by checking bitstream height against
>>>>>> height set before decoding (from container) and then assume interlaced
>>>>>> content and always use top field first (which is wrong IMHO)
>>>>>>
>>>>>> I'll use mov "fiel" atom then, buf if someone store bottom field first
>>>>>> in avi... who knows.
>>>>>>
>>>>> Ping ?
>>>> upload sample videos with top and botom field first 
>>>>
>>> here it is:
>>> mjpeg_top.mov, mjpeg_bottom.mov on mplayerhq.
>> Michael, did you have some time to check this issue ?
> 
> no sorry, far too much to do, this one is rather low priority, and i 
> didnt see a clean solution for it :(

Ok, well it is a bit high priority for me, as it does not decode files
correctly :/

What don't you like in extradata patch ?

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