[FFmpeg-devel] [PATCH] ALS decoder

[Michael Niedermayer]

On Mon, Sep 14, 2009 at 03:23:12PM +0200, Thilo Borgmann wrote:
> Revision 20 attached.
[...]
> +/** Reads the block data for a non-constant block
> + */
> +static int read_var_block(ALSDecContext *ctx, unsigned int ra_block,
> +                          int32_t *raw_samples, unsigned int block_length,
> +                          unsigned int *js_blocks, int32_t *raw_other,
> +                          unsigned int *shift_lsbs)
> +{
> +    ALSSpecificConfig *sconf = &ctx->sconf;
> +    AVCodecContext *avctx    = ctx->avctx;
> +    GetBitContext *gb        = &ctx->gb;
> +    unsigned int k;
> +    unsigned int s[8];
> +    unsigned int sub_blocks, log2_sub_blocks, sb_length;
> +    unsigned int opt_order  = 1;
> +    int32_t      *quant_cof = ctx->quant_cof;
> +    int32_t      *lpc_cof   = ctx->lpc_cof;
> +    unsigned int start      = 0;
> +    int          smp        = 0;
> +    int          sb, store_prev_samples;
> +    int64_t      y;
> +
> +    *js_blocks  = get_bits1(gb);
> +
> +    // determine the number of subblocks for entropy decoding

> +    if (!sconf->bgmc && !sconf->sb_part)
> +        log2_sub_blocks = 0;
> +    else {

should use {}


[...]
> +/** Reads the frame data.
> + */
> +static int read_frame_data(ALSDecContext *ctx, unsigned int ra_frame)
> +{
> +    ALSSpecificConfig *sconf = &ctx->sconf;
> +    AVCodecContext *avctx    = ctx->avctx;
> +    GetBitContext *gb = &ctx->gb;
> +    unsigned int div_blocks[32];                ///< block sizes.
> +    unsigned int c, b;
> +    int32_t *raw_samples_L;
> +    unsigned int js_blocks[2];
> +
> +    uint32_t bs_info = 0;
> +    unsigned int *ptr_div_blocks;
> +
> +    // skip the size of the ra unit if present in the frame
> +    if (sconf->ra_flag == RA_FLAG_FRAMES && ra_frame)
> +        skip_bits_long(gb, 32);
> +
> +    if (sconf->mc_coding && sconf->joint_stereo) {
> +        ctx->js_switch = get_bits1(gb);
> +        align_get_bits(gb);
> +    }
> +
> +    if (!sconf->mc_coding || ctx->js_switch) {
> +        int independent_bs = !sconf->joint_stereo;
> +
> +        for (c = 0; c < avctx->channels; c++) {
> +            js_blocks[0] = 0;
> +            js_blocks[1] = 0;
> +
> +            if (sconf->block_switching) {
> +                unsigned int bs_info_len = 1 << (sconf->block_switching + 2);
> +                bs_info = get_bits_long(gb, bs_info_len);
> +                bs_info <<= (32 - bs_info_len);
> +            }
> +
> +            ctx->num_blocks = 0;
> +            ptr_div_blocks = &div_blocks[0];
> +            parse_bs_info(bs_info, 0, 0, &ptr_div_blocks, &ctx->num_blocks);
> +            reconstruct_block_sizes(ctx, div_blocks);
> +
> +            // if joint_stereo and block_switching is set, independent decoding
> +            // is signaled via the first bit of bs_info
> +            if (sconf->joint_stereo && sconf->block_switching)
> +                if (bs_info >> 31)
> +                    independent_bs = 2;
> +
> +            // if this is the last channel, it has to be decoded independently
> +            if (c == avctx->channels - 1)
> +                independent_bs = 1;
> +
> +            if (independent_bs) {
> +                if (decode_blocks_ind(ctx, ra_frame, c, div_blocks, js_blocks))
> +                    return -1;
> +
> +                if (independent_bs)
> +                    independent_bs--;
> +            } else {
> +                if (decode_blocks(ctx, ra_frame, c, div_blocks, js_blocks))
> +                    return -1;
> +
> +                c++;
> +            }
> +
> +        // store carryover raw samples
> +        memmove(ctx->raw_samples[c] - sconf->max_order,
> +                ctx->raw_samples[c] - sconf->max_order + sconf->frame_length,
> +                sizeof(*ctx->raw_samples[c]) * sconf->max_order);
> +        }
> +    } else { // multi-channel coding

> +        if (sconf->block_switching) {
> +            unsigned int bs_info_len = 1 << (sconf->block_switching + 2);
> +            bs_info = get_bits_long(gb, bs_info_len);
> +            bs_info <<= (32 - bs_info_len);
> +        }
> +
> +        ctx->num_blocks = 0;
> +        ptr_div_blocks = div_blocks;
> +        parse_bs_info(bs_info, 0, 0, &ptr_div_blocks, &ctx->num_blocks);
> +        reconstruct_block_sizes(ctx, div_blocks);

duplicate of the code in the above loop


> +
> +        // TODO: multi channel coding might use a temporary buffer instead as
> +        //       the actual channel is not known when read_block-data is called
> +        raw_samples_L = ctx->raw_samples[0];
> +

> +        for (b = 0; b < ctx->num_blocks; b++) {
> +            if (read_block_data(ctx, ra_frame, raw_samples_L,
> +                                div_blocks[b], &js_blocks[0], NULL)) {
> +                // damaged block, write zero for the rest of the frame
> +                zero_remaining(b, ctx->num_blocks, div_blocks, raw_samples_L);
> +                return -1;
> +            }
> +            raw_samples_L += div_blocks[b];
> +            ra_frame = 0;
> +            // TODO: read_channel_data
> +        }

duplicate of decode_blocks_ind()


[...]
> +/** Scaled PARCOR values used for the first two PARCOR coefficients.
> + *  To be indexed by the Rice coded indices.
> + *  Generated by: parcor_scaled_values[i] = 32 + ((i * (i+1)) << 7) - (1 << 20)
> + */
> +static const int32_t parcor_scaled_values[] = {

fits in int16_t when divided by 32

except these i think your patch should be ok

[..]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Freedom in capitalist society always remains about the same as it was in
ancient Greek republics: Freedom for slave owners. -- Vladimir Lenin
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