[FFmpeg-devel] [PATCH] E-AC-3 decoder, round 3
Justin Ruggles
justin.ruggles
Sun Aug 24 07:25:07 CEST 2008
Michael Niedermayer wrote:
> On Tue, Aug 19, 2008 at 09:16:24PM -0400, Justin Ruggles wrote:
>> Michael Niedermayer wrote:
>>> On Tue, Aug 19, 2008 at 07:43:31PM -0400, Justin Ruggles wrote:
>>>> Michael Niedermayer wrote:
>>>>> On Tue, Aug 19, 2008 at 06:54:35PM -0400, Justin Ruggles wrote:
>>>>>> Hi,
>>>>>>
>>>>>> Thanks for the review.
>>>>>>
>>>>>> Michael Niedermayer wrote:
>>>>>>> On Sun, Aug 17, 2008 at 07:30:26PM -0400, Justin Ruggles wrote:
>>>>>>>> Hi,
>>>>>>>>
>>>>>>>> Here is a new patch to complete support for E-AC-3 decoding within the
>>>>>>>> current AC-3 decoder. It will be followed up by a cosmetic commit to
>>>>>>>> indent and align.
>>>>>>>>
>>>>>>>> -Justin
>>>>>>>>
>>>>>>> [...]
>>>>>>>> @@ -533,10 +547,27 @@
>>>>>>>> }
>>>>>>>> }
>>>>>>>>
>>>>>>>> +static void get_transform_coeffs_ch(AC3DecodeContext *s, int blk, int ch,
>>>>>>>> + mant_groups *m)
>>>>>>>> +{
>>>>>>>> + if (!s->channel_uses_aht[ch]) {
>>>>>>>> + ac3_get_transform_coeffs_ch(s, ch, m);
>>>>>>>> + } else {
>>>>>>>> + /* if AHT is used, mantissas for all blocks are encoded in the first
>>>>>>>> + block of the frame. */
>>>>>>>> + int bin;
>>>>>>>> + if (!blk)
>>>>>>>> + ff_eac3_get_transform_coeffs_aht_ch(s, ch);
>>>>>>> am i blind? or where is this function, i cannot find it in this patch
>>>>>>> nor in svn
>>>>>> oops! I forgot to svn add eac3dec.c. I have attached the whole file
>>>>>> here. It would be applied in the same commit with the rest of these
>>>>>> changes (minus the part you said to commit separately).
>>>>> does any of the changes i ok-ed depend on eac3dec.c ?
>>>>> if not you could commit them and resubmit what is left + eac3dec.c
>>>> Well, sort of. I could apply all the parts OKed so far, but I would
>>>> have to comment out the 2 calls to functions which are in eac3dec.c and
>>>> leave out the part which actually detects the frame as being E-AC-3.
>>> fine
>>> every part commited moves us a step closer to full EAC3 support
>> done. new patch attached.
approved parts have been applied. new patch attached.
>>
>> /* coupling strategy */
>> - if (get_bits1(gbc)) {
>> + if (!s->eac3)
>> + s->cpl_strategy_exists[blk] = get_bits1(gbc);
>> + if (s->cpl_strategy_exists[blk]) {
>
> wouldnt
> if(s->cpl_strategy_exists[blk] || get_bits1(gbc)){
>
> work as well?
fixed.
>> @@ -860,10 +913,14 @@
>> }
>>
>> /* exponent strategies for each channel */
>> - s->exp_strategy[blk][CPL_CH] = EXP_REUSE;
>> - s->exp_strategy[blk][s->lfe_ch] = EXP_REUSE;
>
>> + if (!s->eac3) {
>> + for (ch = !cpl_in_use; ch <= s->channels; ch++) {
>> + s->exp_strategy[blk][ch] = get_bits(gbc, 2 - (ch == s->lfe_ch));
>> + }
>> + }
>> +
>> + /* check exponent strategies to set bit allocation stages */
>> for (ch = !cpl_in_use; ch <= s->channels; ch++) {
>> - s->exp_strategy[blk][ch] = get_bits(gbc, 2 - (ch == s->lfe_ch));
>> if(s->exp_strategy[blk][ch] != EXP_REUSE)
>
> why is that loop seperated? wouldnt a
> if (!s->eac3) in there work as well?
fixed.
>> @@ -924,29 +981,71 @@
>> }
>>
>> /* signal-to-noise ratio offsets and fast gains (signal-to-mask ratios) */
>
>
>> - if (get_bits1(gbc)) {
>> + if (s->snr_offset_strategy && (!s->eac3 || !blk) && get_bits1(gbc)) {
>> + int snr = 0;
>> int csnr;
>> csnr = (get_bits(gbc, 6) - 15) << 4;
>> - for (ch = !cpl_in_use; ch <= s->channels; ch++) { /* snr offset and fast gain */
>> - s->snr_offset[ch] = (csnr + get_bits(gbc, 4)) << 2;
>
>> - s->fast_gain[ch] = ff_ac3_fast_gain_tab[get_bits(gbc, 3)];
> [...]
>> + s->fast_gain[ch] = ff_ac3_fast_gain_tab[get_bits(gbc, 3)];
>
> cosmtic
fixed.
>> + /* run last 2 bit allocation stages if fast gain changes */
>> + if(blk && prev != s->fast_gain[ch])
>> + bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
>> + }
>> }
>> - memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
>> - } else if (!blk) {
>> + } else if (!s->eac3 && !blk) {
>> av_log(s->avctx, AV_LOG_ERROR, "new snr offsets must be present in block 0\n");
>> return -1;
>> }
>
> i was thinking a little about:
>
> if(!s->eac3 || !blk){
> if (s->snr_offset_strategy && get_bits1(gbc)) {
> } else if(!s->eac3 && !blk){
> }
> }
>
> but iam not sure at all if its cleaner or not, just a random idea
fixed.
>> /* coupling leak information */
>> if (cpl_in_use) {
>> - if (get_bits1(gbc)) {
>> + if (s->first_cpl_leak || get_bits1(gbc)) {
>
>> + int prev_fl = s->bit_alloc_params.cpl_fast_leak;
>> + int prev_sl = s->bit_alloc_params.cpl_slow_leak;
>> s->bit_alloc_params.cpl_fast_leak = get_bits(gbc, 3);
>> s->bit_alloc_params.cpl_slow_leak = get_bits(gbc, 3);
>> + /* run last 2 bit allocation stages for coupling channel if
>> + coupling leak changes */
>
>> + if(blk && (prev_fl != s->bit_alloc_params.cpl_fast_leak ||
>> + prev_sl != s->bit_alloc_params.cpl_slow_leak)) {
>> bit_alloc_stages[CPL_CH] = FFMAX(bit_alloc_stages[CPL_CH], 2);
>> + }
>
> i think following is cleaner
>
> int fl= get_bits(gbc, 3);
> int sl= get_bits(gbc, 3);
>
> if(blk && (fl != s->bit_alloc_params.cpl_fast_leak ||
> sl != s->bit_alloc_params.cpl_slow_leak)) {
> bit_alloc_stages[CPL_CH] = FFMAX(bit_alloc_stages[CPL_CH], 2);
> }
> s->bit_alloc_params.cpl_fast_leak = fl;
> s->bit_alloc_params.cpl_slow_leak = sl;
fixed.
>> +
>> +void ff_eac3_get_transform_coeffs_aht_ch(AC3DecodeContext *s, int ch)
>> +{
>> + int bin, blk, gs;
>> + int end_bap, gaq_mode;
>> + GetBitContext *gbc = &s->gbc;
>> + int gaq_gain[AC3_MAX_COEFS];
>> +
>> + gaq_mode = get_bits(gbc, 2);
>> + end_bap = (gaq_mode < 2) ? 12 : 17;
>> +
>> + /* if GAQ gain is used, decode gain codes for bins with hebap between
>> + 8 and end_bap */
>> + gs = 0;
>> + if (gaq_mode == EAC3_GAQ_12 || gaq_mode == EAC3_GAQ_14) {
>> + /* read 1-bit GAQ gain codes */
>> + for (bin = s->start_freq[ch]; bin < s->end_freq[ch]; bin++) {
>> + if (s->bap[ch][bin] > 7 && s->bap[ch][bin] < end_bap)
>> + gaq_gain[gs++] = get_bits1(gbc) << (gaq_mode-1);
>> + }
>> + } else if (gaq_mode == EAC3_GAQ_124) {
>> + /* read 1.67-bit GAQ gain codes (3 codes in 5 bits) */
>> + int gc = 2;
>> + for (bin = s->start_freq[ch]; bin < s->end_freq[ch]; bin++) {
>> + if (s->bap[ch][bin] > 7 && s->bap[ch][bin] < end_bap) {
>> + if (gc++ == 2) {
>> + int group_gain = get_bits(gbc, 5);
>> + gaq_gain[gs++] = ff_ac3_ungroup_3_in_5_bits_tab[group_gain][0];
>> + gaq_gain[gs++] = ff_ac3_ungroup_3_in_5_bits_tab[group_gain][1];
>> + gaq_gain[gs++] = ff_ac3_ungroup_3_in_5_bits_tab[group_gain][2];
>> + gc = 0;
>> + }
>> + }
>> + }
>> + }
>> +
>> + gs=0;
>> + for (bin = s->start_freq[ch]; bin < s->end_freq[ch]; bin++) {
>> + int hebap = s->bap[ch][bin];
>> + int bits = ff_eac3_bits_vs_hebap[hebap];
>> + if (!hebap) {
>> + /* zero-mantissa dithering */
>> + for (blk = 0; blk < 6; blk++) {
>> + s->pre_mantissa[ch][bin][blk] = (av_lfg_get(&s->dith_state) & 0x7FFFFF) - 0x400000;
>> + }
>> + } else if (hebap < 8) {
>> + /* Vector Quantization */
>> + int v = get_bits(gbc, bits);
>> + for (blk = 0; blk < 6; blk++) {
>> + s->pre_mantissa[ch][bin][blk] = ff_eac3_vq_hebap[hebap][v][blk] << 8;
>> + }
>> + } else {
>> + /* Gain Adaptive Quantization */
>> + int gbits, log_gain;
>> + if (gaq_mode != EAC3_GAQ_NO && hebap < end_bap) {
>> + log_gain = gaq_gain[gs++];
>> + } else {
>> + log_gain = 0;
>> + }
>
>> + gbits = bits - log_gain;
>
> this is maybe missing a check for gbits<=0, iam not certain it can happen
> but i think it can
fixed.
>> +
>> + for (blk = 0; blk < 6; blk++) {
>> + int mant = get_sbits(gbc, gbits);
>> + if (mant == -(1 << (gbits-1))) {
>> + /* large mantissa */
>> + int64_t b;
>> + mant = get_sbits(gbc, bits-2+log_gain) << (26-log_gain-bits);
>> + /* remap mantissa value to correct for asymmetric quantization */
>> + if (mant >= 0)
>> + b = 32768 >> log_gain;
>> + else
>> + b = ff_eac3_gaq_remap_2_4_b[hebap-8][log_gain-1];
>> + mant += ((int64_t)ff_eac3_gaq_remap_2_4_a[hebap-8][log_gain-1] * mant + b) >> 15;
>
> this can be done without a 64 bit multiple i think
fixed.
>> + } else {
>> + /* small mantissa, no GAQ, or Gk=1 */
>> + mant <<= 24 - bits;
>> + if (!log_gain) {
>> + /* remap mantissa value for no GAQ or Gk=1 */
>> + mant += ((int64_t)ff_eac3_gaq_remap_1[hebap-8] * mant) >> 15;
>> + }
>
> mant <<= 24 - bits;
> if (!log_gain) {
> /* remap mantissa value for no GAQ or Gk=1 */
> mant = (ff_eac3_gaq_remap_1[hebap-8] * (mant>>8)) >> 7;
> }
fixed.
Thanks,
Justin
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