[FFmpeg-devel] [PATCH] Implement av_samples_fill_arrays().

[Michael Niedermayer]

On Tue, Feb 01, 2011 at 05:18:11PM +0100, Stefano Sabatini wrote:
> On date Tuesday 2011-02-01 16:59:08 +0100, Stefano Sabatini encoded:
> > On date Friday 2011-01-28 21:13:30 +0100, Michael Niedermayer encoded:
> > > On Fri, Jan 28, 2011 at 12:55:09AM +0100, Stefano Sabatini wrote:
> > [...]
> > > > > what iam unsure about is linesize.
> > > > > currently its all set equal, that is mightly useless
> > > > > linesize[0] is as good as linesize[chan]
> > > > > 
> > > > > we could do something more usefull with linesize[1+]
> > > > > like setting it so that
> > > > > linesize[1] = data[1][0] - data[0][0]
> > > > > 
> > > > > the idea is that things could be addressed like
> > > > > data[0] + time*linesize[0] +  chan*linesize[1]
> > > > > the advantage of this over
> > > > > data[chan] + time*linesize[0]
> > > > > is that you need fewer variables (no data[0], data[1], data[2] ...) which can
> > > > > help register starved architectures
> > > > > 
> > > > > 
> > > > > also, if possible a single public function like:
> > > > >  int av_samples_fill_arrays(uint8_t *data[8], int linesizes[8],
> > > > >                             uint8_t *buf, int buf_size,
> > > > >                             enum AVSampleFormat sample_fmt, int planar,
> > > > >                             int nb_channels);
> > > > >
> > > > > that allows data & linesize to be NULL
> > > > > would mean simpler public API thanb having 3 functions
> > > > 
> > > > Done, indeed it's much nicer.
> > > > 
> > > > As for the linesize stuff, I'm wondering if it is better to have
> > > > something more similar to the imgutils stuff, that is to have linesize
> > > > simply give the planar size (for planar) and the buffer size for
> > > > packed (eventually aligned).
> > > > 
> > > > This would be useful for implementing:
> > > > av_samples_copy
> > > > av_samples_alloc
> > > > 
> > > > does it make sense?
> > > 
> > > you have 8 linesize values you set them all equal. you could store differnet
> > > things in there instead of choosing which of 2 usefull values to duplicate 7
> > > times
> > 
> > Updated again, implementing the idea from Michael, other patches
> > attached for reference.
> > 
> > Note that we never defined the semantics of linesizes[] in the
> > AVFilterBuffer for audio samples, the most natural approach is to
> > assume the same semantics used by av_samples_*.
> > 
> > At this point some change is required (in the aconvert) because
> > av_audio_convert() assumes a different semantics for in/out_stride:
> > 
> >  * Convert between audio sample formats
> >  * @param[in] out array of output buffers for each channel. set to NULL to ignore processing of the given channel.
> >  * @param[in] out_stride distance between consecutive output samples (measured in bytes)
> >  * @param[in] in array of input buffers for each channel
> >  * @param[in] in_stride distance between consecutive input samples (measured in bytes)
> >  * @param len length of audio frame size (measured in samples)
> >  */
> > int av_audio_convert(AVAudioConvert *ctx,
> >                            void * const out[6], const int out_stride[6],
> >                      const void * const  in[6], const int  in_stride[6], int len);
> > 
> > Solutions:
> > * create a wrapper in aconvert for converting samplesref->linesize to
> >   in/out_stride semantics.
> > * create an av_audio_convert2() supporting the new semantics
> > 
> > It was discussed some months ago an avcodec_audio_decodeX() which was
> > returning a packet rather than buffer+size as the current API, I
> > suppose that may be relevant for this discussion as well.
> 
> Patch updated with a fix.
> -- 
> FFmpeg = Fiendish and Foolish Mastering Powered Encoding/decoding Guru

>  samplefmt.c |   49 +++++++++++++++++++++++++++++++++++++++++++++++++
>  samplefmt.h |   45 +++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 94 insertions(+)
> bc3a1de65be8467fd8db1f17564f1a0e36f46104  0002-Implement-av_samples_alloc-and-av_samples_fill_array.patch
> From 276363d62c10128cfb86d452e052c9a466f0f931 Mon Sep 17 00:00:00 2001
> From: Stefano Sabatini <stefano.sabatini-lala at poste.it>
> Date: Sat, 15 Jan 2011 00:00:00 +0100
> Subject: [PATCH] Implement av_samples_alloc() and av_samples_fill_arrays().

pushed with some changes, bugfixes and simplification
if you are ok with it we can bump minor & update API-docs

[...]
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