[FFmpeg-devel] [PATCH 13/16] vmdaudio: simplify vmdaudio_decode_frame() by handling block_type first, then making a single call to vmdaudio_loadsound().

[Justin Ruggles]

On 02/22/2011 04:58 PM, Kostya wrote:

> On Tue, Feb 22, 2011 at 02:05:32PM -0500, Justin Ruggles wrote:
>>
>> This also adds output buffer size checks for AUDIO and SILENCE block types.
>> ---
>>  libavcodec/vmdav.c |   24 ++++++++++++------------
>>  1 files changed, 12 insertions(+), 12 deletions(-)
>>
> 
>> diff --git a/libavcodec/vmdav.c b/libavcodec/vmdav.c
>> index 83173d0..92159f6 100644
>> --- a/libavcodec/vmdav.c
>> +++ b/libavcodec/vmdav.c
>> @@ -506,7 +506,7 @@ static int vmdaudio_decode_frame(AVCodecContext *avctx,
>>      const uint8_t *buf = avpkt->data;
>>      int buf_size = avpkt->size;
>>      VmdAudioContext *s = avctx->priv_data;
>> -    int block_type;
>> +    int block_type, silent_chunks;
>>      unsigned char *output_samples = (unsigned char *)data;
>>  
>>      if (buf_size < 16) {
>> @@ -523,23 +523,23 @@ static int vmdaudio_decode_frame(AVCodecContext *avctx,
>>      buf      += 16;
>>      buf_size -= 16;
>>  
>> -    if (block_type == BLOCK_TYPE_AUDIO) {
>> -        /* the chunk contains audio */
>> -        *data_size = vmdaudio_loadsound(s, output_samples, buf, 0, buf_size);
>> -    } else if (block_type == BLOCK_TYPE_INITIAL) {
>> -        /* initial chunk, may contain audio and silence */
>> +    silent_chunks = 0;
>> +    if (block_type == BLOCK_TYPE_INITIAL) {
>>          uint32_t flags = AV_RB32(buf);
>> -        int silent_chunks = av_popcount(flags);
>> +        silent_chunks  = av_popcount(flags);
>>          buf      += 4;
>>          buf_size -= 4;
>> -        if(*data_size < (s->block_align*silent_chunks + buf_size) * 2)
>> -            return -1;
>> -        *data_size = vmdaudio_loadsound(s, output_samples, buf, silent_chunks, buf_size);
>>      } else if (block_type == BLOCK_TYPE_SILENCE) {
>> -        /* silent chunk */
>> -        *data_size = vmdaudio_loadsound(s, output_samples, buf, 1, 0);
>> +        silent_chunks = 1;
>> +        buf_size = 0; // should already be zero but set it just to be sure
>>      }
>>  
>> +    /* ensure output buffer is large enough */
>> +    if (*data_size < (s->block_align*silent_chunks + buf_size) * 2)
>> +        return -1;
>> +
>> +    *data_size = vmdaudio_loadsound(s, output_samples, buf, silent_chunks, buf_size);
>> +
>>      return avpkt->size;
>>  }
>>  
> 
> will it work if initial block needs to interleave silent and non-silent chunks
> in order given by flags?


The structure of the patch will work. Just the silence handling would
have to be changed and flags would have to be passed to
vmdaudio_loadsound().  If you can figure it out, more power to you, but
everything I tried involving interleaving the silence with audio ended
up with silence in very obviously wrong places.

-Justin