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

[Justin Ruggles]

Hi,

Baptiste Coudurier wrote:

> On 7/11/10 9:11 AM, Justin Ruggles wrote:
>> Michael Niedermayer wrote:
>>
>>> On Sun, Jul 11, 2010 at 11:33:25PM +1000, Peter Ross wrote:
>>>> On Sun, Jul 11, 2010 at 11:12:56AM +0100, M?ns Rullg?rd wrote:
>>>>> Peter Ross<pross at xvid.org>  writes:
>>>>>
>>>>>> Hi,
>>>>>>
>>>>>> To prototype use of audio in AVFrame, I have modified the PCM encoder/decoder
>>>>>> and addded new public lavc functions.
>>>>>> [...]
>>>>>> +/**
>>>>>> + * Encode an audio frame from samples into buf.
>>>>>> + *
>>>>>> + * @param avctx the codec context
>>>>>> + * @param[out] buf the output buffer
>>>>>> + * @param[in] buf_size the output buffer size
>>>>>> + * @param[in] frame the input buffer containing the samples
>>>>>> + * @return On error a negative value is returned, on success zero or the number
>>>>>> + * of bytes used to encode the data read from the input buffer.
>>>>>> + */
>>>>>> +int avcodec_encode_audio2(AVCodecContext *avctx, uint8_t *buf, int buf_size,
>>>>>> +                          const AVFrame *frame);
>>>>> At some point, we should do something about the output buffer
>>>>> allocation too.  Currently, a ridiculous size is allocated in ffmpeg.c
>>>>> just to be on the safe side.
>>>> Agree, and should be easy enough to do. Ditto for video, right?
>>> that was discussed previously, in short summary yes but noone did it
>>> Also with encoding into an AVPacket reallocation should be quite easy
>>> as the pointer is easy changeable
>> +1 for me on this.  Sometimes even the ridiculous size is not enough,
>> e.g. FLAC encoding.  The ability to reallocate dynamically if larger
>> frames are created would make things much simpler.
>>
>> I like the overall concept for these changes.  I think it would also get
>> rid of the frame_size=1 for PCM requirement.
> 
> I'm not sure to understand what you mean by frame_size=1 PCM 
> requirement. Can you please elaborate ?

See:

documentation for avcodec_encode_audio() where PCM is handled
differently from other codecs with regard to frame size.

ffmpeg.c:944-1011 where PCM is handled separately from other codecs and
is detected by AVCodecContext.frame_size == 1.

pcm.c:pcm_encode_init() where avctx->frame_size is set to 1.

-Justin