[FFmpeg-devel] [PATCH] WMA Voice decoder

[Vitor Sessak]

Ronald S. Bultje wrote:
> Hi,
> 
> On Tue, Feb 9, 2010 at 1:21 PM, Vitor Sessak <vitor1001 at gmail.com> wrote:
> [..]
>> No, I like the code as it is now, but one thing:
>>
>>>    /*
>>>     * Pitch (per ACB type):
>>>     * - type 0: unused
>>>     * - type 1: provided (globally) for the whole frame. In
>>> #synth_block(),
>>>     *            we derive the "pitch-per-sample" for adaptive codebook
>>>     *            reading.
>>>     * - type 2: provided per block (see just before the call to
>>>     *            #synth_block()), so not read here.
>>>     */
>>>    switch (frame_descs[bd_idx].acb_type) {
>>>    case ACB_TYPE_NONE:
>>>        memset(pitch, 0, sizeof(pitch[0]) * frame_descs[bd_idx].n_blocks);
>>>        break;
>>>    case ACB_TYPE_ASYMMETRIC:
>>>        n_blocks_x2      = frame_descs[bd_idx].n_blocks << 1;
>>>        log_n_blocks_x2  = frame_descs[bd_idx].log_n_blocks + 1;
>>>        cur_pitch_val    = s->min_pitch_val + get_bits(gb, s->pitch_nbits);
>>>        if (s->last_acb_type == ACB_TYPE_NONE ||
>>>            20 * abs(cur_pitch_val - s->last_pitch_val) >
>>>                (cur_pitch_val + s->last_pitch_val))
>>>            s->last_pitch_val = cur_pitch_val;
>>>
>>>        /* pitch per frame/block */
>>>        for (n = 0; n < frame_descs[bd_idx].n_blocks; n++) {
>>>            int fac = n * 2 + 1;
>>>
>>>            pitch[n] = (MUL16(fac,                 cur_pitch_val) +
>>>                        MUL16((n_blocks_x2 - fac), s->last_pitch_val) +
>>>                        frame_descs[bd_idx].n_blocks) >> log_n_blocks_x2;
>>>        }
>> Here you calculate pitch[] for ACB_TYPE_NONE and ACB_TYPE_ASYMMETRIC
>>
>>>    for (n = 0; n < frame_descs[bd_idx].n_blocks; n++) {
>>>        int bl_pitch_sh2 = pitch[n] << 2;
>>>
>>>        /*
>>>         * If pitch is given per block, parse that first. Per-block pitches
>>>         * are encoded as an absolute value for the first block, and then
>>>         * delta values for all subsequent blocks. The scale of this value
>>>         * is semi-logarithmic compared to normal scale, so convert also.
>>>         */
>>>        if (frame_descs[bd_idx].acb_type == ACB_TYPE_HAMMING) {
>>>            int block_pitch,
>>>                t1 = (s->block_conv_table[1] - s->block_conv_table[0]) <<
>>> 2,
>>>                t2 = (s->block_conv_table[2] - s->block_conv_table[1]) <<
>>> 1,
>>>                t3 =  s->block_conv_table[3] - s->block_conv_table[2] + 1;
>>>
>>>            if (n == 0) {
>>>                block_pitch = get_bits(gb, s->block_pitch_nbits);
>>>            } else
>>>                block_pitch = last_block_pitch -
>>> s->block_delta_pitch_hrange +
>>>                                 get_bits(gb, s->block_delta_pitch_nbits);
>>>            /* Convert last_ so that any next delta is within _range */
>>>            last_block_pitch = av_clip(block_pitch,
>>>                                       s->block_delta_pitch_hrange,
>>>                                       s->block_pitch_range -
>>>                                           s->block_delta_pitch_hrange);
>>>
>>>            /* Convert semi-log-style scale back to normal scale */
>>>            if (block_pitch < t1) {
>>>                bl_pitch_sh2 = (s->block_conv_table[0] << 2) + block_pitch;
>>>            } else {
>>>                block_pitch -= t1;
>>>                if (block_pitch < t2) {
>>>                    bl_pitch_sh2 =
>>>                        (s->block_conv_table[1] << 2) + (block_pitch << 1);
>>>                } else {
>>>                    block_pitch -= t2;
>>>                    if (block_pitch < t3) {
>>>                        bl_pitch_sh2 =
>>>                            (s->block_conv_table[2] + block_pitch) << 2;
>>>                    } else
>>>                        bl_pitch_sh2 = s->block_conv_table[3] << 2;
>>>                }
>>>            }
>>>            pitch[n] = bl_pitch_sh2 >> 2;
>>>        }
>> And here you calculate it for ACB_TYPE_HAMMING. It is kind of inconsistent.
> 
> Right, I calculate in order of appearance in the bitstream.

Ugly bitstream format :p

> Would you
> prefer I do the for() loop calculating the asymmetric-acb-pitch within
> the loop that calls synth_block()?

Yes if it is more readable (what I expect).

-Vitor