[FFmpeg-devel] [PATCH] AVCHD/H.264 parser: determination of frame type, question about timestamps

[Ivan Schreter]

Ivan Schreter wrote:
> Hi,
>
> Loren Merritt wrote:
>> On Thu, 22 Jan 2009, Ivan Schreter wrote
>>> Your patch is much more elegant, but I changed the following:
>>>    
>>>> +        case NAL_IDR_SLICE:
>>>> +        case NAL_SLICE:
>>>> +            get_ue_golomb(&h->s.gb);
>>>> +            if(get_ue_golomb(&h->s.gb) % 5 == 2)
>>>> +                s->pict_type= FF_I_TYPE;
>>>> +            else
>>>> +                s->pict_type= FF_P_TYPE;
>>>> +            return;
>>>> +
>>>>       
>>> to this:
>>>
>>> +        case NAL_IDR_SLICE:
>>> +        case NAL_SLICE:
>>> +            get_ue_golomb(&h->s.gb);
>>> +            s->pict_type= 
>>> golomb_to_pict_type[get_ue_golomb(&h->s.gb) % 5];
>>> +            return;
>>>
>>> Reason: Your code didn't correctly set pict_type to FF_B_TYPE for
>>> B-frames, so timing didn't work correctly. Since we already have 
>>> mapping
>>> array, I simply used it to map it instead of adding another if 
>>> statement.
>>>     
>> Certainly frame type should be fixed, but what does this have to do 
>> with timing? H.264 allows any frame types to be reordered, or not, as 
>> the encoder pleases.
>>   
> This part has nothing to do with timing, only with returning proper 
> frame type.
Ah, sorry, to correct myself: It does, indirectly. If picture type is 
not set, it does not know which frame is a B-frame and computes DTS/PTS 
wrong in compute_pkt_fields() heuristics.

Regards,

Ivan