[Mp4-tech] output of deblocking filter

[Robin Zoo]

Dear Gary,
Thank you for your reply!
Maybe I didn't make myself understood. I'd like to ask
my question in a simple way.
First, a H.264 standard compliance encoder is used to
encode an interlaced video clip and make sure that
PAFF and MBAFF are in use. Then a compliance decoder
is used to decode the bit-stream. Is the output of the
decoder a field picture sequence or a mixed field and
frame picture sequence? Is the deblocking filtering
the last decoding step in H.264?
thanks a lot!
Robin
--- Gary Sullivan <garysull windows.microsoft.com>
wrote:
> 
> I believe the answer to this question is not quite
> so simple.  See
> remarks below.
> 
> Best Regards,
> 
> Gary Sullivan 
> 
> +> -----Original Message-----
> +> From: mp4-tech-bounces lists.mpegif.org 
> +> [mailto:mp4-tech-bounces lists.mpegif.org] On
> Behalf Of Robin Zoo
> +> Sent: Wednesday, May 24, 2024 2:16 AM
> +> To: mp4-tech lists.mpegif.org
> +> Subject: [Mp4-tech] output of deblocking filter
> +> 
> +> Dear experts:
> +> 
> +> I noticed the following descriptions in MPEG2
> +> standard:
> +> 
> +> "The output of the decoding process, for
> interlaced
> +> sequences, consists of a series of reconstructed
> +> fields that are separated in time by a field
> period"
> +> 
> +> "In progressive sequences each picture in the
> sequence
> +> shall be a frame picture. The sequence, at the
> output
> +> of the decoding process, consists of a series of
> +> reconstructed frames that are separated in time
> by a
> +> frame period"
> 
> I believe neither of those statements are actually
> necessarily true in
> the MPEG2 low delay mode of operation.  They may be
> true outside of
> low-delay operation.
> 
> 
> +> 
> +> I think the statements are true in H.264 decoding
> +> process though I didn't found similar
> description.
> 
> This is not the case.  My advice is to not try to
> take statements out of
> one standard and apply them to another.  Even if you
> could find some
> case where an out-of-context quote may apply, the
> underlying definitions
> of terms may differ.
> 
> In the case of H.264/MPEG-4 AVC, the output of the
> decoding process is a
> series of pictures.
> Pictures can be frames or fields.
> 
> There is no definition of an "interlaced sequence"
> or a "progressive
> sequence" in H.264/AVC.
> 
> When fixed_frame_rate_flag is equal to 1, there are
> some strict
> constraints on the relative timing of the output of
> pictures in
> H.264/AVC.  When it is not, there aren't.
> 
> Also, I believe there is more of a notion of
> multiple sequences within a
> single bitstream in the case of AVC than there is in
> MPEG-2.
> 
> 
> +> 
> +> Here is my question, for H.264 interlaced
> sequences,
> +> if PAFF and MBAFF are in use, the output of
> deblocking
> +> filter are mixed frame and field pictures which
> even
> +> include frames containing mixed field or frame
> +> macroblock pairs. Interlacing of frame or
> macroblock
> +> pairs has to be done before sending the decoded
> pixel
> +> for display. Is it true?
> 
> It is difficult to understand this question.  
> Anyhow, display is outside of the scope of the
> standard.
> 
> 
> +> 
> +> thanks a lot!
> +> 
> +> Robinstain
> +> 
> +>
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