[FFmpeg-devel] [PATCH] Split reading and decoding of blocks in ALS

[Michael Niedermayer]

On Sat, Nov 14, 2009 at 02:15:30PM +0100, Thilo Borgmann wrote:
> Hi,
> 
> in order to support multi-channel correlation, reading and decoding of a
> block has to be separated. This patch introduces ALSBockData struct for
> that purpose.

[...]
> +/** Decodes the block data for a constant block
> + */
> +static void decode_const_block_data(ALSDecContext *ctx, ALSBlockData *bd)
> +{
> +    int smp;
> +
>      // write raw samples into buffer
> -    for (k = 0; k < block_length; k++)
> -        raw_samples[k] = const_val;
> +    for (smp = 0; smp < bd->block_length; smp++)
> +        bd->raw_samples[smp] = bd->const_val;
>  }

memset32(dst, val, len){
}
would possibly be faster due to not doing bd-> in the loop


[...]
> @@ -553,115 +579,132 @@
>      }
>  
>      if (get_bits1(gb))
> -        *shift_lsbs = get_bits(gb, 4) + 1;
> +        bd->shift_lsbs = get_bits(gb, 4) + 1;
>  
> -    store_prev_samples = (*js_blocks && raw_other) || *shift_lsbs;
> +    bd->store_prev_samples = (bd->js_blocks && bd->raw_other) || bd->shift_lsbs;
>  
> -
>      if (!sconf->rlslms) {
>          if (sconf->adapt_order) {
> -            int opt_order_length = av_ceil_log2(av_clip((block_length >> 3) - 1,
> +            int opt_order_length = av_ceil_log2(av_clip((bd->block_length >> 3) - 1,
>                                                  2, sconf->max_order + 1));
> -            opt_order            = get_bits(gb, opt_order_length);
> +            bd->opt_order        = get_bits(gb, opt_order_length);
>          } else {
> -            opt_order = sconf->max_order;
> +            bd->opt_order = sconf->max_order;
>          }
>  
> -        if (opt_order) {
> +        if (bd->opt_order) {
>              int add_base;
>  
>              if (sconf->coef_table == 3) {
>                  add_base = 0x7F;
>  
>                  // read coefficient 0
> -                quant_cof[0] = 32 * parcor_scaled_values[get_bits(gb, 7)];
> +                bd->quant_cof[0] = 32 * parcor_scaled_values[get_bits(gb, 7)];
>  
>                  // read coefficient 1
> -                if (opt_order > 1)
> -                    quant_cof[1] = -32 * parcor_scaled_values[get_bits(gb, 7)];
> +                if (bd->opt_order > 1)
> +                    bd->quant_cof[1] = -32 * parcor_scaled_values[get_bits(gb, 7)];
>  
>                  // read coefficients 2 to opt_order
> -                for (k = 2; k < opt_order; k++)
> -                    quant_cof[k] = get_bits(gb, 7);
> +                for (k = 2; k < bd->opt_order; k++)
> +                    bd->quant_cof[k] = get_bits(gb, 7);
>              } else {
>                  int k_max;
>                  add_base = 1;
>  
>                  // read coefficient 0 to 19
> -                k_max = FFMIN(opt_order, 20);
> +                k_max = FFMIN(bd->opt_order, 20);
>                  for (k = 0; k < k_max; k++) {
>                      int rice_param = parcor_rice_table[sconf->coef_table][k][1];
>                      int offset     = parcor_rice_table[sconf->coef_table][k][0];
> -                    quant_cof[k] = decode_rice(gb, rice_param) + offset;
> +                    bd->quant_cof[k] = decode_rice(gb, rice_param) + offset;
>                  }
>  
>                  // read coefficients 20 to 126
> -                k_max = FFMIN(opt_order, 127);
> +                k_max = FFMIN(bd->opt_order, 127);
>                  for (; k < k_max; k++)
> -                    quant_cof[k] = decode_rice(gb, 2) + (k & 1);
> +                    bd->quant_cof[k] = decode_rice(gb, 2) + (k & 1);
>  
>                  // read coefficients 127 to opt_order
> -                for (; k < opt_order; k++)
> -                    quant_cof[k] = decode_rice(gb, 1);
> +                for (; k < bd->opt_order; k++)
> +                    bd->quant_cof[k] = decode_rice(gb, 1);
>  
> -                quant_cof[0] = 32 * parcor_scaled_values[quant_cof[0] + 64];
> +                bd->quant_cof[0] = 32 * parcor_scaled_values[bd->quant_cof[0] + 64];
>  
> -                if (opt_order > 1)
> -                    quant_cof[1] = -32 * parcor_scaled_values[quant_cof[1] + 64];
> +                if (bd->opt_order > 1)
> +                    bd->quant_cof[1] = -32 * parcor_scaled_values[bd->quant_cof[1] + 64];
>              }
>  
> -            for (k = 2; k < opt_order; k++)
> -                quant_cof[k] = (quant_cof[k] << 14) + (add_base << 13);
> +            for (k = 2; k < bd->opt_order; k++)
> +                bd->quant_cof[k] = (bd->quant_cof[k] << 14) + (add_base << 13);

it might make sense to have commonly used variables like opt_order on the
stack intead of just accessable through a pointer

besides does this patch lead to any slowdown?

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

The misfortune of the wise is better than the prosperity of the fool.
-- Epicurus
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