[x264-devel] Regarding disabling 4x4 in JM code

[mahesh k]

On 8/7/07, List, Peter <Peter.List at t-systems.com> wrote:
>
>
>   ------------------------------
>
> *Von:* mahesh k [mailto:maheswarreddy.k at gmail.com]
> *Gesendet:* Dienstag, 7. August 2007 14:24
> *An:* Mailing list for x264 developers
> *Betreff:* Re: [x264-devel] Regarding disabling 4x4 in JM code
>
>
>
> Dear peter,
> I am talking about decoder only. I will explain u my problem more clearly.
>
> Right now our decoder works properly with our encoder. Now we need to make
> this decoder standardised in the sense that it should accept any other
> bitstream(for example i want to decode JM encoders output with my decoder).
>
> After reading the syntax elements as per baseline standard I need to check
> whether this is implemented or not in my decoder and return the error still
> needs to be implemented. the intent was that the code shouldnot crash in
> such situations instead return proper error code.
>
> Obviously you will need to decode the COMPLETE mb_type than. For values of
> '0' in Intra-frames and values of '5' in P-Frames and '23' in B-Frames you
> produce your error message.
>
> For I frames if it is o then  I will display error but for P frames
> (slices) thee mb_type should be 0 to 4 as in the table 7.13 Macroblock
> type values o to 4 for P and SP slices . So how can i check for mb_type 5.
> This is as per my knowledge IF i am wrong plz tell me.
>

Also we didnot implement  macroblock partitions  plz tell me how to handle
this situation in case of P frames.

Also plz tell ma how I can generate the encoded bitstream through JM encoder
code. So that I can test my decoder with this bitstream. I disabled 4x4 but
then also its encoding intra4x4_prediction mode.
I understtod ur remaining answers clearly and I thank for that.

> I went through the section that u told me. But my doubts were,
> i dont understand what 0_0_0 signify in name of MB type.
>
> The 1. number in x_x_x  corresponds to column 5 of table 7-11
>
> The 2. number….                                       column  6
>
> The 3. number                                             column 7
>
> Search for the label-text of these table-columns to get their exact
> meaning
>
>
>
> Also in table 7.13 mb_types for P slices, what do we mean by inferred
> type.
>
> *Inferred* means *deduced*. I simply says: if a macroblock does not
> appeare in the bitstream (because it is skipped due to 'mb_skip_run' it
> automatically has the type P_Skip and is 16x16 ….
>
>
> Also tell me can we idetify the prediction mode from mb_type itself?
> Yes, every possible mode is part of the tables! Somewere in 7.4.5 you find
> the note that you have to add the I-Table at the bottom of the P and B
> tables, to signal Intra MB's in P and B-frames.
>
>
>
>
> thanks in advance,
> mahesh.
>
> On 8/7/07, *List, Peter* <Peter.List at t-systems.com> wrote:
>
> Dear Mahesh,
>
> if you are talking about a DECODER intra 4x4 is a must, if you want to be
> standard conform in all cases (for any profile).
>
> If you are talking about  ENCODERS you don't need to implement intra-4x4
> but only use intra-16x16 (resulting in very poor intra performance).
>
>
>
> I don't understand what you mean with:
>
> But we want to decode any standard bitstream that is as per standard but
> return the error code accordingly .
>
> About mb_type read in  "Recommendation H.264" (ISO/IEC 14496-10)
> paragraph 7.4.5
>
>
>
> Peter
>
>
>   ------------------------------
>
> *Von:* mahesh k [mailto:maheswarreddy.k at gmail.com]
> *Gesendet:* Dienstag, 7. August 2007 11:22
> *An:* Mailing list for x264 developers
> *Betreff:* Re: [x264-devel] Regarding disabling 4x4 in JM code
>
>
>
> thanks for ur reply. Plz tell me whether intra 4x4 is must in base line
> profile or it is an optional.
>  Can't we run the baseline profile decoder without 4x4 as per standard?
> I need this because at present we have not implemented this 4x4 mode But
> we want to decode any standard bitstream that is as per standard but return
> the error code accordingly .
> Also I am confused with the syntax element mb_type.
> What values does mb_type should have if i need to check whether this is an
> 4x4 or 16x16.
> Also plz tell me in clear about this mb_type and ma_mde.
> If possible refer some good document on this.
>
> Thanks in advance.
>
> On 8/7/07, *List, Peter* <Peter.List at t-systems.com> wrote:
>
>
> > mahesh k wrote:
> > > I want a baseline ecoded bit stream in which intra4x4 predition mode
> > > should not be present.
> >
> > Note (but you probably already know it): of course intra4x4 is part of
> > baseline.
>
> Also note that intra4x4 is NOT some fancy add on for intra-coding like
> some people think 4x4 motion estimation is.
> Intra4x4 is the basic intra coding mode! It is usually used for the
> majority of intra-macroblocks. Intra-16x16 is only used for very uniform
> macroblocks like blocks from a blue sky or something like that.
> Regards, Peter
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