[FFmpeg-devel] [PATCH] E-AC-3 decoder, round 3

Justin Ruggles justin.ruggles
Sun Aug 31 01:30:55 CEST 2008


Michael Niedermayer wrote:
> On Thu, Aug 28, 2008 at 10:51:26PM -0400, Justin Ruggles wrote:
>> Michael Niedermayer wrote:
>>> On Sun, Aug 24, 2008 at 11:58:23AM -0400, Justin Ruggles wrote:
>>>> 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.
>>>> Updated patch attached with fixes as suggested in ffmpeg-soc mailing list.
>> New patch attached.
>>
>> -Justin
>>
> 
>> Index: libavcodec/ac3dec.c
>> ===================================================================
>> --- libavcodec/ac3dec.c	(revision 15015)
>> +++ libavcodec/ac3dec.c	(working copy)
[...]
>> @@ -769,7 +766,7 @@
>>      /* TODO: spectral extension coordinates */
>>  
>>      /* coupling strategy */
>> -    if (get_bits1(gbc)) {
>> +    if (s->eac3 ? s->cpl_strategy_exists[blk] : get_bits1(gbc)) {
>>          memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
>>          if (!s->eac3)
>>              s->cpl_in_use[blk] = get_bits1(gbc);
>> @@ -855,8 +852,9 @@
>>  
>>          for (ch = 1; ch <= fbw_channels; ch++) {
>>              if (s->channel_in_cpl[ch]) {
>> -                if (get_bits1(gbc)) {
>> +                if ((s->eac3 && s->first_cpl_coords[ch]) || get_bits1(gbc)) {
>>                      int master_cpl_coord, cpl_coord_exp, cpl_coord_mant;
>> +                    s->first_cpl_coords[ch] = 0;
>>                      cpl_coords_exist = 1;
>>                      master_cpl_coord = 3 * get_bits(gbc, 2);
>>                      for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
>> @@ -872,6 +870,9 @@
>>                      av_log(s->avctx, AV_LOG_ERROR, "new coupling coordinates must be present in block 0\n");
>>                      return -1;
>>                  }
>> +            } else {
>> +                /* channel not in coupling */
>> +                s->first_cpl_coords[ch] = 1;
>>              }
> 
> ok

applied.

> 
>>          }
>>          /* phase flags */
>> @@ -960,18 +961,35 @@
>>      }
>>  
>>      /* signal-to-noise ratio offsets and fast gains (signal-to-mask ratios) */
>> -    if (get_bits1(gbc)) {
>> +    if(!s->eac3 || !blk){
>> +        if(s->snr_offset_strategy && 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;
>> +        for (i = ch = !cpl_in_use; ch <= s->channels; ch++) {
>> +            /* snr offset */
>> +            if (ch == i || s->snr_offset_strategy == 2)
>> +                snr = (csnr + get_bits(gbc, 4)) << 2;
>> +            /* run at least last bit allocation stage if snr offset changes */
>> +            if(blk && s->snr_offset[ch] != snr) {
>> +                bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 1);
>> +            }
>> +            s->snr_offset[ch] = snr;
>> +
>> +                /* fast gain (normal AC-3 only) */
>> +                if (!s->eac3) {
>> +                    int prev = s->fast_gain[ch];
>>              s->fast_gain[ch] = ff_ac3_fast_gain_tab[get_bits(gbc, 3)];
>> -        }
>> -        memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
>> -    } else if (!blk) {
>> +                    /* 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);
>> +                    }
>> +                }
> 
>> +    } else if (!s->eac3 && !blk) {
> 
> this can never be true, as its truth implicates the if() above being
> true

I don't see it. Maybe the indentation made it hard to read. I've changed
it for the new patch. Let me know if I'm just missing something here...

> 
>>          av_log(s->avctx, AV_LOG_ERROR, "new snr offsets must be present in block 0\n");
>>          return -1;
>>      }
>> +    }
>>  
>>      /* fast gain (E-AC-3 only) */
>>      if (s->fast_gain_syntax && get_bits1(gbc)) {
>> @@ -994,14 +1012,22 @@
>>  
>>      /* coupling leak information */
>>      if (cpl_in_use) {
>> -        if (get_bits1(gbc)) {
>> -            s->bit_alloc_params.cpl_fast_leak = get_bits(gbc, 3);
>> -            s->bit_alloc_params.cpl_slow_leak = get_bits(gbc, 3);
>> +        if (s->first_cpl_leak || get_bits1(gbc)) {
>> +            int fl = get_bits(gbc, 3);
>> +            int sl = get_bits(gbc, 3);
>> +            /* run last 2 bit allocation stages for coupling channel if
>> +               coupling leak changes */
> 
>> +            if(blk && (fl != s->bit_alloc_params.cpl_fast_leak ||
>> +                    sl != s->bit_alloc_params.cpl_slow_leak)) {
> 
> these can be vertically aligned

fixed.

> 
>>              bit_alloc_stages[CPL_CH] = FFMAX(bit_alloc_stages[CPL_CH], 2);
>> -        } else if (!blk) {
>> +            }
>> +            s->bit_alloc_params.cpl_fast_leak = fl;
>> +            s->bit_alloc_params.cpl_slow_leak = sl;
>> +        } else if (!s->eac3 && !blk) {
>>              av_log(s->avctx, AV_LOG_ERROR, "new coupling leak info must be present in block 0\n");
>>              return -1;
>>          }
>> +        s->first_cpl_leak = 0;
>>      }
>>  
>>      /* delta bit allocation information */
>> Index: libavcodec/Makefile
>> ===================================================================
>> --- libavcodec/Makefile	(revision 15015)
>> +++ libavcodec/Makefile	(working copy)
>> @@ -27,7 +27,7 @@
>>  
>>  OBJS-$(CONFIG_AAC_DECODER)             += aac.o aactab.o mdct.o fft.o
>>  OBJS-$(CONFIG_AASC_DECODER)            += aasc.o
>> -OBJS-$(CONFIG_AC3_DECODER)             += ac3dec.o ac3tab.o ac3dec_data.o ac3.o mdct.o fft.o
>> +OBJS-$(CONFIG_AC3_DECODER)             += eac3dec.o ac3dec.o ac3tab.o ac3dec_data.o ac3.o mdct.o fft.o
>>  OBJS-$(CONFIG_AC3_ENCODER)             += ac3enc.o ac3tab.o ac3.o
>>  OBJS-$(CONFIG_ALAC_DECODER)            += alac.o
>>  OBJS-$(CONFIG_ALAC_ENCODER)            += alacenc.o lpc.o
> 
>> Index: libavcodec/eac3dec.c
>> ===================================================================
>> --- libavcodec/eac3dec.c	(revision 15015)
>> +++ libavcodec/eac3dec.c	(working copy)
>> @@ -78,3 +78,414 @@
>>      pre_mant[4] = even1 - odd1;
>>      pre_mant[5] = even0 - odd0;
>>  }
>> +
>> +void ff_eac3_decode_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++) {
> 
> ok
> 
> 
>> +            if (s->bap[ch][bin] > 7 && s->bap[ch][bin] < end_bap) {
> 
> end_bap is guranteed to be 17 here, ok otherwise

fixed and applied.

> 
>> [remainder of the file]
> 
> ok

applied.

new patch attached.

thanks,
Justin

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