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

[Michael Niedermayer]

On Mon, Nov 23, 2009 at 11:28:35AM +0100, Thilo Borgmann wrote:
> Michael Niedermayer schrieb:
> > 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
> 
> Ok will do...
> 
> 
> > 
> > [...]
> >> @@ -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
> 
> Yes.
> 
> > besides does this patch lead to any slowdown?
> 
> The benchmark results showed a little slowdown but at least hardly
> noticable on the command line...
> We had this issue at the soc list. Ended up with me providing some
> assembler file grep results for checking inlining done by the compiler.

was the slowdown fixed or not?
"not" is bad

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Let us carefully observe those good qualities wherein our enemies excel us
and endeavor to excel them, by avoiding what is faulty, and imitating what
is excellent in them. -- Plutarch
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