[FFmpeg-devel] [PATCH+RFC] AVFrame for audio

Michael Niedermayer michaelni
Wed Nov 24 19:00:12 CET 2010


On Sat, Nov 13, 2010 at 01:13:09PM -0500, Justin Ruggles wrote:
> Michael Niedermayer wrote:
> 
> > On Mon, Nov 01, 2010 at 05:19:00PM -0400, Justin Ruggles wrote:
> >> Michael Niedermayer wrote:
> >>
> >>> On Sat, Oct 30, 2010 at 08:06:42AM -0400, Justin Ruggles wrote:
> >>>> Michael Niedermayer wrote:
> >>>>
> >>>>> On Thu, Oct 28, 2010 at 06:58:11PM -0400, Justin Ruggles wrote:
> >>>>>> Michael Niedermayer wrote:
> >>>>>>
> >>>>>>> On Wed, Oct 27, 2010 at 10:13:10PM -0400, Justin Ruggles wrote:
> >>>>>>>> Michael Niedermayer wrote:
> >>>>>>>>
> >>>>>>>>> On Tue, Oct 26, 2010 at 09:31:13PM -0400, Justin Ruggles wrote:
> >>>>>>>>>> Michael Niedermayer wrote:
> >>>>>>>>>>
> >>>>>>>>>>> On Sun, Oct 17, 2010 at 05:22:54PM -0400, Justin Ruggles wrote:
> >>>>>>>>>>>> Michael Niedermayer wrote:
> >>>>>>>>>>>>
> >>>>>>>>>>>>> On Sat, Oct 16, 2010 at 04:12:26PM -0400, Justin Ruggles wrote:
> >>>>>>>>>>>>>> Michael Niedermayer wrote:
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> On Fri, Oct 15, 2010 at 06:35:01PM -0400, Justin Ruggles wrote:
> >>>>>>>>>>>>>>>> Justin Ruggles wrote:
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> Michael Niedermayer wrote:
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> On Wed, Oct 13, 2010 at 07:52:12PM -0400, Justin Ruggles wrote:
> >>>>>>>>>>>>>>>>>>> Michael Niedermayer wrote:
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>> On Wed, Oct 06, 2010 at 11:05:26AM -0400, Justin Ruggles wrote:
> >>>>>>>>>>>>>>>>>>>>> Michael Niedermayer wrote:
> >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>> On Tue, Oct 05, 2010 at 04:55:12PM -0400, Justin Ruggles wrote:
> >>>>>>>>>>>>>>>>>>>>>>> Michael Niedermayer wrote:
> >>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>>> On Wed, Sep 29, 2010 at 09:20:04PM -0400, Justin Ruggles wrote:
> >>>>>>>>>>>>>>>>>>>>>>>>> Hi,
> >>>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>>>> Peter Ross wrote:
> >>>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>>>>> On Thu, Sep 02, 2010 at 07:11:37PM -0400, Justin Ruggles wrote:
> >>>>>>>>>>>>>>>>>>>>>>>>>>> Hi,
> >>>>>>>>>>>>>>>>>>>> [...]
> >>>>>>>>>>>>>>>>>>>>>>>> [...]
> >>>>>>>>>>>>>>>>>>>>>>>>> @@ -644,29 +677,49 @@
> >>>>>>>>>>>>>>>>>>>>>>>>>  }
> >>>>>>>>>>>>>>>>>>>>>>>>>  #endif
> >>>>>>>>>>>>>>>>>>>>>>>>>  
> >>>>>>>>>>>>>>>>>>>>>>>>> +#if LIBAVCODEC_VERSION_MAJOR < 53
> >>>>>>>>>>>>>>>>>>>>>>>>>  int attribute_align_arg avcodec_decode_audio3(AVCodecContext *avctx, int16_t *samples,
> >>>>>>>>>>>>>>>>>>>>>>>>>                           int *frame_size_ptr,
> >>>>>>>>>>>>>>>>>>>>>>>>>                           AVPacket *avpkt)
> >>>>>>>>>>>>>>>>>>>>>>>>>  {
> >>>>>>>>>>>>>>>>>>>>>>>>> +    AVFrame frame;
> >>>>>>>>>>>>>>>>>>>>>>>>> +    int ret, got_frame = 0;
> >>>>>>>>>>>>>>>>>>>>>>>>> +
> >>>>>>>>>>>>>>>>>>>>>>>>> +    avcodec_get_frame_defaults(&frame);
> >>>>>>>>>>>>>>>>>>>>>>>>> +
> >>>>>>>>>>>>>>>>>>>>>>>>> +    ret = avcodec_decode_audio4(avctx, &frame, &got_frame, avpkt);
> >>>>>>>>>>>>>>>>>>>>>>>>> +
> >>>>>>>>>>>>>>>>>>>>>>>>> +    if (ret >= 0 && got_frame) {
> >>>>>>>>>>>>>>>>>>>>>>>>> +        *frame_size_ptr = frame.nb_samples * avctx->channels *
> >>>>>>>>>>>>>>>>>>>>>>>>> +                          (av_get_bits_per_sample_format(avctx->sample_fmt) / 8);
> >>>>>>>>>>>>>>>>>>>>>>>>> +
> >>>>>>>>>>>>>>>>>>>>>>>>> +        /* ensure data will fit in the output buffer */
> >>>>>>>>>>>>>>>>>>>>>>>>> +        if (*frame_size_ptr > AVCODEC_MAX_AUDIO_FRAME_SIZE) {
> >>>>>>>>>>>>>>>>>>>>>>>>> +            av_log(avctx, AV_LOG_WARNING, "avcodec_decode_audio3 samples "
> >>>>>>>>>>>>>>>>>>>>>>>>> +                   "truncated to AVCODEC_MAX_AUDIO_FRAME_SIZE\n");
> >>>>>>>>>>>>>>>>>>>>>>>>> +            *frame_size_ptr = AVCODEC_MAX_AUDIO_FRAME_SIZE;
> >>>>>>>>>>>>>>>>>>>>>>>>> +        }
> >>>>>>>>>>>>>>>>>>>>>>>>> +
> >>>>>>>>>>>>>>>>>>>>>>>>> +        memcpy(samples, frame.data[0], *frame_size_ptr);
> >>>>>>>>>>>>>>>>>>>>>>>>  the default get_buffer() should return the appropriate
> >>>>>>>>>>>>>>>>>>>>>>>> buffer for this case.
> >>>>>>>>>>>>>>>>>>>>>>> I'm sorry, I don't understand your comment.
> >>>>>>>>>>>>>>>>>>>>>> i mean (non functional psseudocode below to explain the idea)
> >>>>>>>>>>>>>>>>>>>>>> avcodec_decode_audio3(){
> >>>>>>>>>>>>>>>>>>>>>>     avctx->foobar= samples;
> >>>>>>>>>>>>>>>>>>>>>>     ret = avcodec_decode_audio4(avctx, &frame, &got_frame, avpkt);
> >>>>>>>>>>>>>>>>>>>>>>     ...
> >>>>>>>>>>>>>>>>>>>>>>     assert(samples == frame.data[0]);
> >>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>> -----
> >>>>>>>>>>>>>>>>>>>>>> default_get_buffer(){
> >>>>>>>>>>>>>>>>>>>>>>     if(avctx->foobar)
> >>>>>>>>>>>>>>>>>>>>>>         return avctx->foobar;
> >>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>> (and yes this cannot work for all theoretical decoders)
> >>>>>>>>>>>>>>>>>>>>> I think I get it.  So avctx->foobar would be an optional user-supplied
> >>>>>>>>>>>>>>>>>>>>> buffer (avctx->user_buffer?) that default_get_buffer() would return if
> >>>>>>>>>>>>>>>>>>>>> it is non-NULL, right?
> >>>>>>>>>>>>>>>>>>>> yes
> >>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>> The problem I see is this:
> >>>>>>>>>>>>>>>>>>>>> avcodec_decode_audio3() would use avcodec_decode_audio4().
> >>>>>>>>>>>>>>>>>>>>> avcodec_decode_audio4() allocates as large a buffer as is needed through
> >>>>>>>>>>>>>>>>>>>>> get_buffer(), but the avcodec_decode_audio3() API only requires the
> >>>>>>>>>>>>>>>>>>>>> user-supplied buffer to be AVCODEC_MAX_AUDIO_FRAME_SIZE.  Couldn't this
> >>>>>>>>>>>>>>>>>>>>> lead to the decoder writing past the end of a user-supplied buffer if it
> >>>>>>>>>>>>>>>>>>>>> isn't large enough?  I guess we could also add a field
> >>>>>>>>>>>>>>>>>>>>> avctx->user_buffer_size?
> >>>>>>>>>>>>>>>>>>>> yes, of course
> >>>>>>>>>>>>>>>>>>>> it was just a rough idea ...
> >>>>>>>>>>>>>>>>>>> I'm running into some questions trying to implement the rough idea.  The
> >>>>>>>>>>>>>>>>>>> only way I can see this working smoothly is if avcodec_decode_audio3()
> >>>>>>>>>>>>>>>>>>> always sets get/release_buffer to default.  Also, either all audio
> >>>>>>>>>>>>>>>>>>> decoders will have to support CODEC_CAP_DR1 (i.e. they always use
> >>>>>>>>>>>>>>>>>>> get/release_buffer) or there needs to be a fallback that will memcpy
> >>>>>>>>>>>>>>>>>>> into the user buffer if CODEC_CAP_DR1 is not supported.
> >>>>>>>>>>>>>>>>>> old API decoders surely dont need to copy with old API.
> >>>>>>>>>>>>>>>>>> old API decoders surely dont need to copy with new API if the api can provide
> >>>>>>>>>>>>>>>>>> a buffer to the decoder (this can be through function argument like its done
> >>>>>>>>>>>>>>>>>> currently)
> >>>>>>>>>>>>>>>>>> new API decoders surely dont need to copy with new API because otherwise the
> >>>>>>>>>>>>>>>>>> API sucks and needs more work
> >>>>>>>>>>>>>>>>>> whats left is new API decoders and used with old API and for this get_buffer()
> >>>>>>>>>>>>>>>>>> should return the user supplied buffer if its large enough and fail if its not
> >>>>>>>>>>>>>>>>>> large enough.
> >>>>>>>>>>>>>>>>>> The case where the user overrides get_buffer() and supplies a user specified
> >>>>>>>>>>>>>>>>>> buffer which its own code doesnt use is a case that id consider user error.
> >>>>>>>>>>>>>>>>> I think I might have been misinterpreting the API.  For video decoders,
> >>>>>>>>>>>>>>>>> what does it mean as far as buffer allocation when CODEC_CAP_DR1 is not set?
> >>>>>>>>>>>>>>>> So I think I have this worked out and I don't see how we can avoid a
> >>>>>>>>>>>>>>>> memcpy with the old API when CODEC_CAP_DR1 is not set.  There would be
> >>>>>>>>>>>>>>>> no other way to get the data into the correct output buffer.
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> other questions:
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> 1. Should AVCodecContext.user_buffer be supported for video decoders?
> >>>>>>>>>>>>>>> possible but this is seperate, lets not entangle this patch with too many
> >>>>>>>>>>>>>>> other changes
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> If so, should it be user_buffer[4] and user_buffer_size[4]?
> >>>>>>>>>>>>>>> possible
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> 2. avcodec_default_get_buffer() supports allocating multiple internal
> >>>>>>>>>>>>>>>> buffers.  How should that be handled if the buffer is supplied by the
> >>>>>>>>>>>>>>>> user?  Don't support multiple buffers?  Use the user-supplied buffer
> >>>>>>>>>>>>>>>> just for the first one?
> >>>>>>>>>>>>>>> there are buffer hints (grep for hint in avcodec.h) that specify if a buffer
> >>>>>>>>>>>>>>> will be reused/read/preserved/blah
> >>>>>>>>>>>>>>> the user supplied buffer is likely just valid for this call and cannot be used
> >>>>>>>>>>>>>>> for some cases of the hints. For what remains using the buffer on the first
> >>>>>>>>>>>>>>> call only seems ok
> >>>>>>>>>>>>>> I think I've implemented it in a way that will work even when the
> >>>>>>>>>>>>>> various buffer hints are set.  This implementation will not use memcpy
> >>>>>>>>>>>>>> in avcodec_decode_audio3() in the most common case of the decoder
> >>>>>>>>>>>>>> supporting CODEC_CAP_DR1, only needing 1 buffer, and not needing a
> >>>>>>>>>>>>>> buffer larger than AVCODEC_MAX_AUDIO_FRAME_SIZE.
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>> One thing I'm unsure of is whether to truncate output if it is too large
> >>>>>>>>>>>>>> for avcodec_decode_audio3() (which is done in this patch) or to return
> >>>>>>>>>>>>>> an error instead.
> >>>>>>>>>>>>> I think its better to tell the user straight through an error that there is a
> >>>>>>>>>>>>> problem instead of generating output that contains randomly truncated packets
> >>>>>>>>>>>> Ok. New patch.
> >>>>>>>>>>>>
> >>>>>>>>>>>> -Justin
> >>>>>>>>>>> [...]
> >>>>>>>>>>>>  int avcodec_default_get_buffer(AVCodecContext *s, AVFrame *pic){
> >>>>>>>>>>>>      int i;
> >>>>>>>>>>>>      int w= s->width;
> >>>>>>>>>>>>      int h= s->height;
> >>>>>>>>>>>> +    int is_video = (s->codec_type == AVMEDIA_TYPE_VIDEO);
> >>>>>>>>>>>>      InternalBuffer *buf;
> >>>>>>>>>>>>      int *picture_number;
> >>>>>>>>>>>>  
> >>>>>>>>>>>> @@ -235,7 +258,8 @@ int avcodec_default_get_buffer(AVCodecContext *s, AVFrame *pic){
> >>>>>>>>>>>>          return -1;
> >>>>>>>>>>>>      }
> >>>>>>>>>>>>  
> >>>>>>>>>>>> -    if(av_image_check_size(w, h, 0, s))
> >>>>>>>>>>>> +    if(( is_video && av_image_check_size(w, h, 0, s)) ||
> >>>>>>>>>>>> +       (!is_video && audio_check_size(s->channels, pic->nb_samples, s->sample_fmt)))
> >>>>>>>>>>>>          return -1;
> >>>>>>>>>>>>  
> >>>>>>>>>>>>      if(s->internal_buffer==NULL){
> >>>>>>>>>>>> @@ -253,17 +277,30 @@ int avcodec_default_get_buffer(AVCodecContext *s, AVFrame *pic){
> >>>>>>>>>>>>      picture_number= &(((InternalBuffer*)s->internal_buffer)[INTERNAL_BUFFER_SIZE]).last_pic_num; //FIXME ugly hack
> >>>>>>>>>>>>      (*picture_number)++;
> >>>>>>>>>>>>  
> >>>>>>>>>>>> -    if(buf->base[0] && (buf->width != w || buf->height != h || buf->pix_fmt != s->pix_fmt)){
> >>>>>>>>>>>> +    if (buf->base[0]) {
> >>>>>>>>>>>> +        if (is_video && (buf->width != w || buf->height != h || buf->pix_fmt != s->pix_fmt)){
> >>>>>>>>>>>>          for(i=0; i<4; i++){
> >>>>>>>>>>>>              av_freep(&buf->base[i]);
> >>>>>>>>>>>>              buf->data[i]= NULL;
> >>>>>>>>>>>>          }
> >>>>>>>>>>>> +        } else if (!is_video && (buf->channels   != s->channels     ||
> >>>>>>>>>>>> +                                 buf->nb_samples != pic->nb_samples ||
> >>>>>>>>>>>> +                                 buf->sample_fmt != s->sample_fmt)) {
> >>>>>>>>>>>> +            if (buf->base[0] == s->user_buffer) {
> >>>>>>>>>>>> +                s->user_buffer_in_use = 0;
> >>>>>>>>>>>> +                buf->base[0] = NULL;
> >>>>>>>>>>>> +            } else {
> >>>>>>>>>>>> +                av_freep(&buf->base[0]);
> >>>>>>>>>>>> +            }
> >>>>>>>>>>>> +            buf->data[0] = NULL;
> >>>>>>>>>>>> +        }
> >>>>>>>>>>>>      }
> >>>>>>>>>>>>  
> >>>>>>>>>>>>      if(buf->base[0]){
> >>>>>>>>>>>>          pic->age= *picture_number - buf->last_pic_num;
> >>>>>>>>>>>>          buf->last_pic_num= *picture_number;
> >>>>>>>>>>>>      }else{
> >>>>>>>>>>>> +        if (is_video) {
> >>>>>>>>>>>>          int h_chroma_shift, v_chroma_shift;
> >>>>>>>>>>>>          int size[4] = {0};
> >>>>>>>>>>>>          int tmpsize;
> >>>>>>>>>>>> @@ -327,6 +364,28 @@ int avcodec_default_get_buffer(AVCodecContext *s, AVFrame *pic){
> >>>>>>>>>>>>          buf->height = s->height;
> >>>>>>>>>>>>          buf->pix_fmt= s->pix_fmt;
> >>>>>>>>>>>>          pic->age= 256*256*256*64;
> >>>>>>>>>>>> +        } else { /* audio */
> >>>>>>>>>>>> +            int buf_size;
> >>>>>>>>>>>> +
> >>>>>>>>>>>> +            buf->last_pic_num = -256*256*256*64;
> >>>>>>>>>>>> +
> >>>>>>>>>>>> +            buf_size = pic->nb_samples * s->channels *
> >>>>>>>>>>>> +                       (av_get_bits_per_sample_format(s->sample_fmt) / 8);
> >>>>>>>>>>>> +
> >>>>>>>>>>>> +            if (s->user_buffer && !s->user_buffer_in_use && s->user_buffer_size >= buf_size) {
> >>>>>>>>>>>> +                buf->base[0] = s->user_buffer;
> >>>>>>>>>>>> +                s->user_buffer_in_use = 1;
> >>>>>>>>>>>> +            } else {
> >>>>>>>>>>>> +                buf->base[0] = av_mallocz(buf_size);
> >>>>>>>>>>>> +                if (!buf->base[0])
> >>>>>>>>>>>> +                    return AVERROR(ENOMEM);
> >>>>>>>>>>>> +            }
> >>>>>>>>>>>> +
> >>>>>>>>>>>> +            buf->data[0]    = buf->base[0];
> >>>>>>>>>>>> +            buf->channels   = s->channels;
> >>>>>>>>>>>> +            buf->nb_samples = pic->nb_samples;
> >>>>>>>>>>>> +            buf->sample_fmt = s->sample_fmt;
> >>>>>>>>>>>> +        }
> >>>>>>>>>>>>      }
> >>>>>>>>>>>>      pic->type= FF_BUFFER_TYPE_INTERNAL;
> >>>>>>>>>>>>
> >>>>>>>>>>>> @@ -360,9 +419,15 @@ void avcodec_default_release_buffer(AVCodecContext *s, AVFrame *pic){
> >>>>>>>>>>>>      }
> >>>>>>>>>>>>      assert(i < s->internal_buffer_count);
> >>>>>>>>>>>>      s->internal_buffer_count--;
> >>>>>>>>>>>> +    if (buf->base[0] == s->user_buffer) {
> >>>>>>>>>>>> +        assert(s->user_buffer_in_use);
> >>>>>>>>>>>> +        s->user_buffer_in_use = 0;
> >>>>>>>>>>>> +        buf->base[0] = NULL;
> >>>>>>>>>>>> +    } else {
> >>>>>>>>>>>>      last = &((InternalBuffer*)s->internal_buffer)[s->internal_buffer_count];
> >>>>>>>>>>>>  
> >>>>>>>>>>>>      FFSWAP(InternalBuffer, *buf, *last);
> >>>>>>>>>>>> +    }
> >>>>>>>>>>>>  
> >>>>>>>>>>>>      for(i=0; i<4; i++){
> >>>>>>>>>>>>          pic->data[i]=NULL;
> >>>>>>>>>>> i dont see how this could work
> >>>>>>>>>>> the buffer used and returned by the previous decode() is put in a que by the
> >>>>>>>>>>> user app and user_buffer is set to a new buffer.
> >>>>>>>>>>> also you appear to end up calling av_free()
> >>>>>>>>>>> on user supplied buffers
> >>>>>>>>>> Well, I meant to disallow that, but the documentation I put just says
> >>>>>>>>>> the user cannot free or change the data while user_buffer_in_use is set.
> >>>>>>>>>>  I didn't consider the user replacing it with a new buffer.  But at any
> >>>>>>>>>> rate, if that should be allowed, things get more complicated.  I'll need
> >>>>>>>>>> to add a flag or something to indicate each user-supplied buffer.  I'll
> >>>>>>>>>> work on it.
> >>>>>>>>> i think the API is too complex already and i dont see why it is so
> >>>>>>>>> if user buffer is set get_buffer() should return it or fail, if its returned
> >>>>>>>>> it should set user_buffer to NULL
> >>>>>>>>> calling get_buffer() a second time if user_buffer was set should be disallowed
> >>>>>>>>> release_buffer should do nothing
> >>>>>>>>>
> >>>>>>>>> if we ever have decoders that dont work with this then we need a AVCodec flag
> >>>>>>>>> that indicates them. For this case get_buffer() would then ignore user_buffer
> >>>>>>>>> and avcodec_decode() would copy to the provided user_buffer if any.
> >>>>>>>>> (we do not need this currently though because we do not have such a decoder)
> >>>>>>>>>
> >>>>>>>>> maybe iam missing something but this seems simpler
> >>>>>>>> Ok I did it a different way.  New patch attached.  I'm not 100% sure
> >>>>>>>> about the way reget_buffer() is handled but it works.  AVFrame.type
> >>>>>>>> seems to be a mask, but I don't know if it was intended to be used that way.
> >>>>>>>>
> >>>>>>>> Cheers,
> >>>>>>>> Justin
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>  doc/APIchanges       |    9 ++
> >>>>>>>>  libavcodec/avcodec.h |  100 ++++++++++++++++++++++++++++++--
> >>>>>>>>  libavcodec/pcm.c     |   41 +++++++++++--
> >>>>>>>>  libavcodec/utils.c   |  157 ++++++++++++++++++++++++++++++++++++++++++++-------
> >>>>>>>>  4 files changed, 275 insertions(+), 32 deletions(-)
> >>>>>>>> 39eb7fb791089c0822e3f87d3226b49131563a72  avcodec_decode_audio4.patch
> >>>>>>>> diff --git a/doc/APIchanges b/doc/APIchanges
> >>>>>>>> index 4155d32..a39d9fd 100644
> >>>>>>>> --- a/doc/APIchanges
> >>>>>>>> +++ b/doc/APIchanges
> >>>>>>>> @@ -13,6 +13,15 @@ libavutil:   2009-03-08
> >>>>>>>>  
> >>>>>>>>  API changes, most recent first:
> >>>>>>>>  
> >>>>>>>> +2010-XX-XX - rXXXXX - lavc 52.92.0 - AVFrame and avcodec_decode_audio
> >>>>>>>> +  Add nb_samples field to AVFrame.
> >>>>>>>> +  Add user_buffer, user_buffer_size, and user_buffer_in_use fields to AVCodecContext.
> >>>>>>>> +  Deprecate AVCODEC_MAX_AUDIO_FRAME_SIZE.
> >>>>>>>> +  Deprecate avcodec_decode_audio3() in favor of avcodec_decode_audio4().
> >>>>>>>> +  avcodec_decode_audio4() writes output samples to an AVFrame, which gives the
> >>>>>>>> +  audio decoders the ability to use get/release/reget_buffer() to get an
> >>>>>>>> +  output buffer.
> >>>>>>>> +
> >>>>>>>>  2010-10-10 - r25441 - lavfi 1.49.0 - AVFilterLink.time_base
> >>>>>>>>    Add time_base field to AVFilterLink.
> >>>>>>>>  
> >>>>>>>> diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
> >>>>>>>> index 4bddbaa..1aa1c8c 100644
> >>>>>>>> --- a/libavcodec/avcodec.h
> >>>>>>>> +++ b/libavcodec/avcodec.h
> >>>>>>>> @@ -31,7 +31,7 @@
> >>>>>>>>  #include "libavutil/cpu.h"
> >>>>>>>>  
> >>>>>>>>  #define LIBAVCODEC_VERSION_MAJOR 52
> >>>>>>>> -#define LIBAVCODEC_VERSION_MINOR 92
> >>>>>>>> +#define LIBAVCODEC_VERSION_MINOR 93
> >>>>>>>>  #define LIBAVCODEC_VERSION_MICRO  0
> >>>>>>>>  
> >>>>>>>>  #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \
> >>>>>>>> @@ -467,8 +467,10 @@ enum SampleFormat {
> >>>>>>>>                                            CH_FRONT_LEFT_OF_CENTER|CH_FRONT_RIGHT_OF_CENTER)
> >>>>>>>>  #define CH_LAYOUT_STEREO_DOWNMIX    (CH_STEREO_LEFT|CH_STEREO_RIGHT)
> >>>>>>>>  
> >>>>>>>> +#if FF_API_AUDIO_OLD
> >>>>>>>>  /* in bytes */
> >>>>>>>>  #define AVCODEC_MAX_AUDIO_FRAME_SIZE 192000 // 1 second of 48khz 32bit audio
> >>>>>>>> +#endif
> >>>>>>>>  
> >>>>>>>>  /**
> >>>>>>>>   * Required number of additionally allocated bytes at the end of the input bitstream for decoding.
> >>>>>>>> @@ -988,7 +990,13 @@ typedef struct AVPanScan{
> >>>>>>>>       * - decoding: Set by libavcodec\
> >>>>>>>>       */\
> >>>>>>>>      void *hwaccel_picture_private;\
> >>>>>>>> -
> >>>>>>>> +\
> >>>>>>>> +    /**\
> >>>>>>>> +     * number of audio samples (per channel) described by this frame\
> >>>>>>>> +     * - encoding: Set by user.\
> >>>>>>>> +     * - decoding: Set by libavcodec.\
> >>>>>>>> +     */\
> >>>>>>>> +    int nb_samples;\
> >>>>>>>>  
> >>>>>>>>  #define FF_QSCALE_TYPE_MPEG1 0
> >>>>>>>>  #define FF_QSCALE_TYPE_MPEG2 1
> >>>>>>>> @@ -2744,6 +2752,33 @@ typedef struct AVCodecContext {
> >>>>>>>>       * - decoding: unused
> >>>>>>>>       */
> >>>>>>>>      int lpc_passes;
> >>>>>>>> +
> >>>>>>>> +    /**
> >>>>>>>> +     * User-allocated audio decoder output buffer & buffer size
> >>>>>>>> +     * If user_buffer is non-NULL and is large enough,
> >>>>>>>> +     * avcodec_default_get_buffer() may user it as an internal buffer instead
> >>>>>>>> +     * of allocating its own. This only works with decoders that support
> >>>>>>>> +     * CODEC_CAP_DR1. If the decoder uses this buffer, it will set the value
> >>>>>>>> +     * to NULL.
> >>>>>>>> +     *
> >>>>>>>> +     * @note The user may not use this field when using avcodec_decode_audio3()
> >>>>>>>> +     *       or avcodec_decode_audio2().
> >>>>>>> I dont see why we need such special casing. *samples could be passed in the new
> >>>>>>> api like it is in the old
> >>>>>> The old API already has the samples buffer passed directly.  Why should
> >>>>>> the old API be changed to accept user_buffer as an alternative to
> >>>>>> *samples?  Do they have to match?  If not, which takes priority?  This
> >>>>>> would require added documentation to an old API.  That seems more
> >>>>>> complexity than necessary when the ability to supply a direct buffer is
> >>>>>> already there.
> >>>>> you misunderstand
> >>>>> why is the new api having it passed over AVCodecContext and the old over an
> >>>>> function argument (in the sense why dont you change the new api to also take
> >>>>> a argument for that?) maybe i miss something but this seems to be simpler
> >>>> Ah, thanks for clarifying.
> >>>>
> >>>> The new API doesn't need it.  The old API needs it in order to avoid
> >>>> memcpy.  In the new API, if the user wants a direct buffer, she can
> >>>> override get/release_buffer().
> >>> she can but that is more code and work
> >> Ok.  I'm somewhat against it, but I'm willing to implement it.
> > 
> > can you elaborate on why you are against it?
> > to me this looks nicer and more logic from the outsides users point of view
> 
> I would feel better about it if we have something in the documentation
> saying that not passing a direct buffer is the preferred usage since it
> will ensure that a large enough buffer will be allocated as long as
> enough memory is available and the audio parameters are within a sane range.

The documentation can be changed ...
[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I know you won't believe me, but the highest form of Human Excellence is
to question oneself and others. -- Socrates
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