Re: [Iaxclient-devel] Theora: problematic frame (slices)

[Paulo V. <vic...@gm...>]

Hi Mihai,
First I'll try to set key frame frequency to 2^3 (to use an Intra-coded
picture after 8-1 predictive-coded pictures) -Thus 8/15s between them or
other values to that.

Do you know if theora will have a built in support for slices as well as
picture type (P,B) loss/detection mechanism?
Thank you

Paulo

On Tue, Sep 23, 2008 at 1:01 PM, Mihai Balea <mi...@ha...> wrote:

> Hi Paulo,
>
> The current deslicer code does drop incomplete frames, you can check
> lib/slice.c.  As for out of order slices, the jitterbuffer in iaxclient
> should help re-order them and the deslicer itself has some primitive
> re-ordering features.
>
> The problem, however, goes deeper than that.  With most video codecs,
> Theora included, only key frames (i-frames) are independent, all other
> frames (p-frames) depend on the previous ones to display correctly.  So if
> you lose one frame, all the following p-frames up to the next key frame will
> display incorrectly.  Some codecs, like H.264 are designed to cope with the
> loss of some frame fragments, but unfortunately Theora has no such
> provisions.  There is no easy way to fix this, the only reasonable solution
> is to increase the key frame frequency so that the codec at least recovers
> quickly enough. Right now,  iaxclient sets the key frame frequency to 1 per
> second, you can change that in codec_theora.c, in codec_video_theora_new().
>
> As an alternative, you could try to freeze video until a new keyframe
> arrives, but that might be actually worse than the problem. It might require
> some changes in codec_theora.c and slice.c, but you could experiment with
> it, see what works for you.
>
> Hope this helps,
>
> Mihai
>
>
> On Sep 23, 2008, at 11:15 AM, Paulo Vicentini wrote:
>
>  Hi,
>> I am using 2.1beta3 with video support (theora codec).
>> Sometimes I am getting (probably due network actions- packet loss / delay)
>> a distortion in the video image degrading its quality and I think it is
>> something related to the video slices / chunks (dropped or disordered) of
>> the entire frame.
>> Is there a way to detect a "problematic frame" - whose chunks are missing
>> or disordered and drop it rather than display it?
>>
>> Thanks
>>
>> Paulo
>>
>>
>>
>>
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