[FFmpeg-devel] [PATCH] ALAC Encoder

[Ramiro Polla]

Michael Niedermayer wrote:
> On Tue, Aug 19, 2008 at 01:09:07AM +0530, Jai Menon wrote:
>> Hi,
>>
>> On Monday 18 Aug 2008 3:46:23 am Michael Niedermayer wrote:

[...]

>> Index: libavcodec/alacenc.c
>> ===================================================================
>> --- libavcodec/alacenc.c	(revision 14824)
>> +++ libavcodec/alacenc.c	(working copy)
>> @@ -38,6 +38,11 @@
>>  #define ALAC_MAX_LPC_PRECISION    9
>>  #define ALAC_MAX_LPC_SHIFT        9
>>  
>> +#define ALAC_CHMODE_LEFT_RIGHT    0
>> +#define ALAC_CHMODE_LEFT_SIDE     1
>> +#define ALAC_CHMODE_RIGHT_SIDE    2
>> +#define ALAC_CHMODE_MID_SIDE      3
>> +
>>  typedef struct RiceContext {
>>      int history_mult;
>>      int initial_history;
>> @@ -53,9 +58,12 @@
>>  
>>  typedef struct AlacEncodeContext {
>>      int compression_level;
>> +    int min_prediction_order;
>> +    int max_prediction_order;
>>      int max_coded_frame_size;
>>      int write_sample_size;
>>      int32_t sample_buf[MAX_CHANNELS][DEFAULT_FRAME_SIZE];
>> +    int32_t predictor_buf[DEFAULT_FRAME_SIZE];
>>      int interlacing_shift;
>>      int interlacing_leftweight;
>>      PutBitContext pbctx;
>> @@ -116,6 +124,20 @@
>>      put_bits(&s->pbctx, 32, s->avctx->frame_size);          // No. of samples in the frame
>>  }
>>  
>> +static void calc_predictor_params(AlacEncodeContext *s, int ch)
>> +{
>> +    int32_t coefs[MAX_LPC_ORDER][MAX_LPC_ORDER];
>> +    int shift[MAX_LPC_ORDER];
>> +    int opt_order;
>> +
>> +    opt_order = ff_lpc_calc_coefs(&s->dspctx, s->sample_buf[ch], s->avctx->frame_size, DEFAULT_MIN_PRED_ORDER, DEFAULT_MAX_PRED_ORDER,
>> +                                   ALAC_MAX_LPC_PRECISION, coefs, shift, 1, ORDER_METHOD_EST, ALAC_MAX_LPC_SHIFT, 1);
>> +
>> +    s->lpc[ch].lpc_order = opt_order;
>> +    s->lpc[ch].lpc_quant = shift[opt_order-1];
>> +    memcpy(s->lpc[ch].lpc_coeff, coefs[opt_order-1], opt_order*sizeof(int));
>> +}
>> +
>>  static int estimate_stereo_mode(int32_t *left_ch, int32_t *right_ch, int n)
>>  {
>>      int i, best;
>> @@ -147,7 +169,163 @@
>>              best = i;
>>          }
>>      }
>> +    return best;
>> +}
>>  
>> +static void alac_stereo_decorrelation(AlacEncodeContext *s)
>> +{
>> +    int32_t *left = s->sample_buf[0], *right = s->sample_buf[1];
>> +    int i, mode, n = s->avctx->frame_size;
>> +    int32_t tmp;
>> +
>> +    mode = estimate_stereo_mode(left, right, n);
>> +
>> +    switch(mode)
>> +    {
>> +        case ALAC_CHMODE_LEFT_RIGHT:
>> +            s->interlacing_leftweight = 0;
>> +            s->interlacing_shift = 0;
>> +            break;
>> +
>> +        case ALAC_CHMODE_LEFT_SIDE:
>> +            for(i=0; i<n; i++) {
>> +                right[i] = left[i] - right[i];
>> +            }
>> +            s->interlacing_leftweight = 1;
>> +            s->interlacing_shift = 0;
>> +            break;
>> +
>> +        case ALAC_CHMODE_RIGHT_SIDE:
>> +            for(i=0; i<n; i++) {
>> +                tmp = right[i];
>> +                right[i] = left[i] - right[i];
>> +                left[i] = tmp + (right[i] >> 31);
>> +            }
>> +            s->interlacing_leftweight = 1;
>> +            s->interlacing_shift = 31;
>> +            break;
>> +
>> +        default:
>> +            for(i=0; i<n; i++) {
>> +                tmp = left[i];
>> +                left[i] = (tmp + right[i]) >> 1;
>> +                right[i] = tmp - right[i];
>> +            }
>> +            s->interlacing_leftweight = 1;
>> +            s->interlacing_shift = 1;
>> +            break;
>> +    }
>> +}
> 
> ok

Applied.

[...]
>> @@ -226,6 +404,32 @@
>>          AV_WB8(alac_extradata+20, s->rc.k_modifier);
>>      }
>>  
>> +    if(avctx->min_prediction_order >= 0) {
>> +        if(avctx->min_prediction_order < MIN_LPC_ORDER ||
>> +            avctx->min_prediction_order > MAX_LPC_ORDER) {
>> +            av_log(avctx, AV_LOG_ERROR, "invalid min prediction order: %d\n", avctx->min_prediction_order);
>> +                return -1;
>> +        }
>> +
>> +        s->min_prediction_order = avctx->min_prediction_order;
>> +    }
>> +
>> +    if(avctx->max_prediction_order >= 0) {
>> +        if(avctx->max_prediction_order < MIN_LPC_ORDER ||
>> +           avctx->max_prediction_order > MAX_LPC_ORDER) {
>> +            av_log(avctx, AV_LOG_ERROR, "invalid max prediction order: %d\n", avctx->max_prediction_order);
>> +                return -1;
>> +        }
>> +
>> +        s->max_prediction_order = avctx->max_prediction_order;
>> +    }
>> +
>> +    if(s->max_prediction_order < s->min_prediction_order) {
>> +        av_log(avctx, AV_LOG_ERROR, "invalid prediction orders: min=%d max=%d\n",
>> +               s->min_prediction_order, s->max_prediction_order);
>> +        return -1;
>> +    }
>> +
>>      avctx->extradata = alac_extradata;
>>      avctx->extradata_size = ALAC_EXTRADATA_SIZE;
>>  
>> @@ -255,6 +459,9 @@
>>          return -1;
>>      }
>>  
>> +verbatim:
>> +    init_put_bits(pb, frame, buf_size);
>> +
>>      if((s->compression_level == 0) || verbatim_flag) {
>>          // Verbatim mode
>>          int16_t *samples = data;
> 
> ok

Applied.