[FFmpeg-devel] [PATCH 03/20] lavc: Add coded bitstream read/write API

[Michael Niedermayer]

On Thu, Oct 12, 2017 at 12:35:35AM +0100, Mark Thompson wrote:
> On 11/10/17 23:34, Michael Niedermayer wrote:
> > Hi
> > 
> > On Mon, Oct 09, 2017 at 08:04:47PM +0100, Mark Thompson wrote:
> > [...]
> > 
> >> diff --git a/libavcodec/cbs.h b/libavcodec/cbs.h
> >> new file mode 100644
> >> index 0000000000..e35175fc74
> >> --- /dev/null
> >> +++ b/libavcodec/cbs.h
> >> @@ -0,0 +1,283 @@
> >> +/*
> >> + * This file is part of FFmpeg.
> >> + *
> >> + * FFmpeg is free software; you can redistribute it and/or
> >> + * modify it under the terms of the GNU Lesser General Public
> >> + * License as published by the Free Software Foundation; either
> >> + * version 2.1 of the License, or (at your option) any later version.
> >> + *
> >> + * FFmpeg is distributed in the hope that it will be useful,
> >> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> >> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> >> + * Lesser General Public License for more details.
> >> + *
> >> + * You should have received a copy of the GNU Lesser General Public
> >> + * License along with FFmpeg; if not, write to the Free Software
> >> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
> >> + */
> >> +
> >> +#ifndef AVCODEC_CBS_H
> >> +#define AVCODEC_CBS_H
> >> +
> >> +#include <stddef.h>
> >> +#include <stdint.h>
> >> +
> >> +#include "avcodec.h"
> >> +
> 
> (Here)
> 
> >> +
> >> +struct CodedBitstreamType;
> >> +
> > 
> >> +/**
> >> + * The codec-specific type of a bitstream unit.
> >> + */
> >> +typedef uint32_t CodedBitstreamUnitType;
> > 
> > Whats a bitstream unit ? (no iam not asking you to explain me but it
> > should be documeted)
> 
> See the comment ten lines below this one.
> 
> > Is there some high level overview of this API and its components ?
> > I mean without having to search terms in dispersed documentation.
> > 
> > The high level documentation should also explain what this API does
> > in a terse and clear way.
> > Maybe something like: (if thats correct)
> > Converts between a bit/byte stream and object tree representation of
> > a frame.
> > The (serialized) bitstream representation is what is commonly stored
> > in containers and passed around on networks. The object tree
> > representation allows easier modification of individual elements.
> 
> Inserted at "Here" above:
> 
> /*
>  * This defines a framework for converting between a coded bitstream
>  * and structures defining all individual syntax elements found in
>  * such a stream.
>  *
>  * Conversion in both directions is possible.  Given a coded bitstream
>  * (any meaningful fragment), it can be parsed and decomposed into
>  * syntax elements stored in a set of codec-specific structures.
>  * Similarly, given a set of those same codec-specific structures the
>  * syntax elements can be serialised and combined to create a coded
>  * bitstream.
>  */

[...]

> >> +/**
> >> + * Read the data bitstream from a packet into a fragment, then
> >> + * split into units and decompose.
> >> + */
> >> +int ff_cbs_read_packet(CodedBitstreamContext *ctx,
> >> +                       CodedBitstreamFragment *frag,
> >> +                       const AVPacket *pkt);

maybe ff_cbs_decompose_packet() would be a better name ?

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

No snowflake in an avalanche ever feels responsible. -- Voltaire
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