[FFmpeg-soc] [soc]: r5408 - in als: als_data.h alsdec.c

[Justin Ruggles]

thilo.borgmann wrote:

> Author: thilo.borgmann
> Date: Tue Oct 13 21:35:21 2009
> New Revision: 5408
> 
> Log:
> Added long-term prediction.
> 
> Modified:
>    als/als_data.h
>    als/alsdec.c
> 
> Modified: als/als_data.h
> ==============================================================================
> --- als/als_data.h	Tue Oct 13 21:29:01 2009	(r5407)
> +++ als/als_data.h	Tue Oct 13 21:35:21 2009	(r5408)
> @@ -92,4 +92,11 @@ static const int16_t parcor_scaled_value
>  };
>  
>  
> +/** Gain values of p(0) for long-term prediction.
> + *  To be indexed by the Rice coded indices.
> + */
> +static const int ltp_gain [] = {
> +    0, 8, 16, 24, 32, 40, 48, 56, 64, 70, 76, 82, 88, 92, 96, 100
> +};


uint8_t

> +
>  #endif /* AVCODEC_ALS_DATA_H */
> 
> Modified: als/alsdec.c
> ==============================================================================
> --- als/alsdec.c	Tue Oct 13 21:29:01 2009	(r5407)
> +++ als/alsdec.c	Tue Oct 13 21:35:21 2009	(r5408)
> @@ -79,6 +79,7 @@ typedef struct {
>      unsigned int frame_id;          ///< the frame ID / number of the current frame
>      unsigned int js_switch;         ///< if true, joint-stereo decoding is enforced
>      unsigned int num_blocks;        ///< number of blocks used in the current frame
> +    int ltp_lag_length;             ///< number of bits used for ltp lag value
>      int32_t *quant_cof;             ///< quantized parcor coefficients
>      int32_t *lpc_cof;               ///< coefficients of the direct form prediction filter
>      int32_t *prev_raw_samples;      ///< contains unshifted raw samples from the previous block
> @@ -290,7 +291,6 @@ static int check_specific_config(ALSDecC
>      }
>  
>      MISSING_ERR(sconf->floating,             "Floating point decoding",     -1);
> -    MISSING_ERR(sconf->long_term_prediction, "Long-term prediction",        -1);
>      MISSING_ERR(sconf->bgmc,                 "BGMC entropy decoding",       -1);
>      MISSING_ERR(sconf->mc_coding,            "Multi-channel correlation",   -1);
>      MISSING_ERR(sconf->rlslms,               "Adaptive RLS-LMS prediction", -1);
> @@ -470,6 +470,9 @@ static int read_var_block(ALSDecContext 
>      int          smp        = 0;
>      int          sb, store_prev_samples;
>      int64_t      y;
> +    int          use_ltp    = 0;
> +    int          lag        = 0;
> +    int          gain[5];


for clarity, you should maybe call those ltp_lag and ltp_gain.

>  
>      *js_blocks  = get_bits1(gb);
>  
> @@ -568,7 +571,26 @@ static int read_var_block(ALSDecContext 
>          }
>      }
>  
> -    // TODO: LTP mode
> +    // read LTP gain and lag values
> +    if (sconf->long_term_prediction) {
> +        use_ltp = get_bits1(gb);
> +
> +        if (use_ltp) {
> +            gain[0]   = decode_rice(gb, 1) << 3;
> +            gain[1]   = decode_rice(gb, 2) << 3;
> +
> +            gain[2]   = get_unary(gb, 0, 4);
> +            gain[2] <<= 2;
> +            gain[2]  += get_bits(gb, 2);
> +            gain[2]   = ltp_gain[gain[2]];
> +
> +            gain[3]   = decode_rice(gb, 2) << 3;
> +            gain[4]   = decode_rice(gb, 1) << 3;
> +
> +            lag       = get_bits(gb, ctx->ltp_lag_length);
> +            lag      += FFMAX(4, opt_order + 1);
> +        }
> +    }
>  
>      // read first value and residuals in case of a random access block
>      if (ra_block) {
> @@ -593,6 +615,26 @@ static int read_var_block(ALSDecContext 
>                  *current_res++ = decode_rice(gb, s[sb]);
>       }
>  
> +    // revert long-term prediction


I would use "reverse" or "inverse" instead of "revert".

> +    if (use_ltp) {
> +        int ltp_smp;
> +
> +        for (ltp_smp = 0; ltp_smp < block_length; ltp_smp++) {
> +            int center = ltp_smp - lag;
> +            int begin  = FFMAX(0, center - 2);
> +            int end    = center + 3;
> +            int tab    = 5 - (end - begin);
> +            int base;
> +
> +            y = 1 << 6;
> +
> +            for (base = begin; base < end; base++, tab++)
> +                y += MUL64(gain[tab], raw_samples[base]);
> +
> +            raw_samples[ltp_smp] += y >> 7;
> +        }
> +    }


Maybe you could calculate the point where begin < end so that you don't
have a lot of unneeded raw_samples[ltp_smp] += 0.

Good job.  I assume it works with conformance test samples?

-Justin