[FFmpeg-devel] [PATCH] Mimic decoder

[Ramiro Polla]

Hello Vitor,

[...]

>>     return 1;
>> }
>>
>> static void prepare_avpic(MimicContext *ctx, AVPicture *dst, AVPicture *src)
>> {
>>     int i;
>>     dst->data[0] = src->data[0]+( ctx->avctx->height    -1)*src->linesize[0];
>>     dst->data[1] = src->data[2]+((ctx->avctx->height>>1)-1)*src->linesize[2];
>>     dst->data[2] = src->data[1]+((ctx->avctx->height>>1)-1)*src->linesize[1];
>>     for(i = 0 ; i < 3 ; i++)
>>         dst->linesize[i] = -src->linesize[i];
>> }
> 
> Maybe adding a comment:
> 
> /**
>   * Flip the buffer upside-down and put it in the YVU order to match the
>   * way Mimic encodes frames.
>   */
> static void prepare_avpic(MimicContext *ctx, AVPicture *dst, AVPicture *src)

Added.

>> static int decode(MimicContext *ctx, int quality, int num_coeffs,
>>                   int is_pframe)
>> {
>>     int y, x, plane, offset;
>>     DECLARE_ALIGNED_16(DCTELEM, dct_block[64]);
>>     uint8_t *src, *dst, *p;
>>     AVPicture cur_frame;
>>     AVPicture prev_frame;
>>     uint8_t *base_src;
>>     uint8_t *base_dst;
>>
>>     prepare_avpic(ctx, &cur_frame , (AVPicture*) &ctx->picture   );
>>     prepare_avpic(ctx, &prev_frame, (AVPicture*) &ctx->prev_frame);
>>
>>     for(plane = 0; plane < 3; plane++) {
>>         const int is_chroma = !!plane;
>>         const int qscale = is_chroma ? av_clip(10000-quality, 1000, 10000)<<2 :
>>                                        av_clip(10000-quality, 2000, 10000)<<2 ;
> 
> const int qscale =
>      av_clip(10000-quality, is_chroma ? 1000 : 2000, 10000)<<2;
> 
> or more obfuscated
> 
> const int qscale =
>      av_clip(10000-quality, 2000 >> is_chroma, 10000)<<2;

I chose the less obfuscated approach =)

>>         const int stride = cur_frame.linesize[plane];
>>         base_src = prev_frame.data[plane];
>>         base_dst = cur_frame. data[plane];
>>         offset = 0;
>>         for(y = 0 ; y < ctx->num_vblocks[plane] ; y++) {
>>             unsigned int num_rows = 8;
>>             /* The last row of blocks in chrominance for 160x120 resolution
>>              * is half the normal height and must be accounted for. */
>>             if(is_chroma &&
>>                y + 1 == ctx->num_vblocks[plane] && ctx->avctx->height & 15)
>>                 num_rows = 4;
>>             src = base_src + offset;
>>             dst = base_dst + offset;
> 
> uint8_t *src = base_src + offset;
> uint8_t *dst = base_dst + offset;

Done. And a few more...

> [...]
> 
>>     21, 21, 21, 22, 22, 22, 22, 23, 23, 23, 23,  0,
>>      6, 10, 24, 24, 24, 24, 25, 25, 25, 25, 26, 26,
>>     26, 26, 27,  0, 10, 27, 27, 27, 28, 28, 28, 28,
>>     29, 29, 29, 29, 30, 30, 30,
>> };
>>
>> /*
>>  * initialize_vlcdec_lookup
>>  *
>>  * Internal helper-function used to initialize
>>  * the lookup-table used by the VLC-decoder.
>>  */
>> static void initialize_vlcdec_lookup(int8_t lookup_tbl[8][128])
> 
> /**
>   * Internal helper-function used to initialize
>   * the lookup-table used by the VLC-decoder.
>   */
> static void initialize_vlcdec_lookup(int8_t lookup_tbl[8][128])
> 
> If this function do not go away...

I think I'll drop them...

Thanks,
Ramiro Polla