[FFmpeg-devel] [PATCH] lavfi audio framework

[S.N. Hemanth Meenakshisundaram]

On 07/30/2010 01:29 AM, Stefano Sabatini wrote:
> On date Thursday 2010-07-22 01:18:36 -0700, S.N. Hemanth Meenakshisundaram encoded:
>   
>> [...]
>>  #define MAX_REGISTERED_AVFILTERS_NB 64
>>  
>>  static AVFilter *registered_avfilters[MAX_REGISTERED_AVFILTERS_NB + 1];
>> diff --git a/libavfilter/avfilter.h b/libavfilter/avfilter.h
>> index a9bec02..faeb3b6 100644
>> --- a/libavfilter/avfilter.h
>> +++ b/libavfilter/avfilter.h
>> @@ -38,6 +38,7 @@
>>  
>>  #include <stddef.h>
>>  #include "libavcodec/avcodec.h"
>> +#include "libavcodec/audioconvert.h"
>>  
>>  /**
>>   * Return the LIBAVFILTER_VERSION_INT constant.
>> @@ -66,7 +67,7 @@ typedef struct AVFilterPad     AVFilterPad;
>>   */
>>  typedef struct AVFilterBuffer
>>  {
>> -    uint8_t *data[8];           ///< buffer data for each plane
>> +    uint8_t *data[8];           ///< buffer data for each plane/channel
>>      int linesize[8];            ///< number of bytes per line
>>      int format;                 ///< media format
>>  
>> @@ -130,6 +131,32 @@ static inline void avfilter_copy_picref_props(AVFilterPicRef *dst, AVFilterPicRe
>>  }
>>  
>>  /**
>> + * A reference to an AVFilterBuffer for audio. Since filters can manipulate the
>> + * origin of an audio buffer to, for example, reduce precision without any memcpy,
>> + * sample format and channel_layout are per-reference properties. Sample step is
>> + * also useful when reducing the number of channels, etc, and so is also per-reference.
>> + */
>> +typedef struct AVFilterSamplesRef
>> +{
>> +    AVFilterBuffer *samples;      ///< the audio buffer that this is a reference to
>> +    uint8_t *data[8];             ///< audio data for each channel
>> +    int linesize[8];              ///< number of bytes to next sample
>> +    int64_t pts;                  ///< presentation timestamp in units of 1/AV_TIME_BASE
>> +
>> +    int64_t channel_layout;       ///< channel layout of current buffer
>> +    int64_t sample_rate;          ///< samples per second
>> +    enum SampleFormat sample_fmt; ///< sample format
>> +
>> +    int samples_nb;               ///< number of samples in this buffer
>> +    /* Should this go here or in the AVFilterBuffer struct? */
>> +    int size;                     ///< size of buffer
>> +
>> +    int perms;                    ///< permissions
>> +
>> +    int planar;                   ///< is buffer planar or packed
>> +} AVFilterSamplesRef;
>>     
> The alternative here if we don't want to duplicate the generic fields:
> AVFilterBuffer -> actually contains the data
>
> AVFilterBufferRef[erence] in place of AVFilterSamplesRef and
> AVFilterSamplesPic.
>
> Then we may share the common fields (perms, size, pts, buffer, data,
> linesize), use a media type field and put the media specific stuff in
> an union.
>
> This requires more work to re-adapt the patch, but will avoid evil
> code duplication.
>
> Michael?
>
> Same technique may be used for AVFilterLink.
>
> [...]
>
> Regards.
>   

I noticed that sample_rate is only an int or uint32_t in other places,
will change it in lavfi too to uint32_t. Also 'int format' can be moved
from AVFilterBuffer to AVFilterPicRef since SamplesRef already has it
and only two filters (vsrc_buffer and vf_overlay) need to be changed to
use format field in PicRef instead of AVFilterBuffer.

Also I need to add pos to AVFilterSamplesRef.

With those two changes, things should fit nicely into unions and making
AVFilterBufferRef will be simpler.

pic/samples, data, linesize, format, pts, pos and perms common,
AVRational pixel_aspect(2 integers) in PicRef and channel layout (int64)
in SamplesRef forming a union,

4 other ints in PicRef (w, h, interlaced, top_field_first) and 4 ints in
SamplesRef (samples_nb, size, planar and sample_rate).

Can I go ahead with this?

Regards,