Ronald S. Bultje wrote:
> Hi Mark,
>
> On Tue, Jan 27, 2009 at 4:25 AM, Mark Kenna
> <[email protected]> wrote:
>
>> I'm wondering the best way to handle B-Frames within the MPEG4 stream
>> when you don't have access to the PTS or DTS value's (check previous posts).
>> Currently I am thinking of just reading the GOP which is sent as [I P B
>> B B P B B B] and reordering the frames into [I B B B P B B B P] and then
>> displaying them and carrying on...
>>
>> What I would like to know is:
>> a) is it a good idea to handle them this way? (probably not)
>>
>
> No.
>
I have implemented a solution that "kind of" uses the above method and
works very well. I will just post it as a possible alternative to
relying on libav* to correctly realign the frames - especially when you
do not have access to AVFormatContext and/or av_read_frame(..).
I populate a List with decoded Frames as they arrive on the stream, once
I have read three frames I do the following:
do
{
frameList.add(newestFrame);
if (frameList.Count == 3)
{
switch (frameList[0].PictType)
{
case I_FRAME:
{
DrawPicture(frameList[0]);
frameList.RemoveAt(0);
break;
}
case P_FRAME:
{
if ((frameList[1].PictType ==
P_FRAME) || (frameList[1].PictType == I_FRAME))
{
DrawPicture(frameList[0]);
frameList.RemoveAt(0);
}
else
{
Frame tempFrame = frameList[0];
frameList[0] = frameList[1];
frameList[1] = tempFrame;
}
break;
}
case B_FRAME:
{
DrawPicture(frameList[0]);
frameList.RemoveAt(0);
break;
}
}
}
} while(reading);
I understand fully that this is not the correct way to do this kind of
decoding, but under my circumstances I don't think I have any other option.
I hope this helps someone.
Thanks for the help guys,
Mark.
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