alac.c

tcpmp播放器的flv插件

    /* otherwise basic interlacing took place */
    for (i = 0; i < numsamples; i++) {
        int16_t left, right;

        left = buffer_a[i];
        right = buffer_b[i];

        buffer_out[i*numchannels] = left;
        buffer_out[i*numchannels + 1] = right;
    }
}

static int alac_decode_frame(AVCodecContext *avctx,
                             void *outbuffer, int *outputsize,
                             uint8_t *inbuffer, int input_buffer_size)
{
    ALACContext *alac = avctx->priv_data;

    int channels;
    int32_t outputsamples;

    /* short-circuit null buffers */
    if (!inbuffer || !input_buffer_size)
        return input_buffer_size;

    /* initialize from the extradata */
    if (!alac->context_initialized) {
        if (alac->avctx->extradata_size != ALAC_EXTRADATA_SIZE) {
            av_log(NULL, AV_LOG_ERROR, "alac: expected %d extradata bytes\n", 
                ALAC_EXTRADATA_SIZE);
            return input_buffer_size;
        }
        alac_set_info(alac);
        alac->context_initialized = 1;
    }

    outputsamples = alac->setinfo_max_samples_per_frame;

    init_get_bits(&alac->gb, inbuffer, input_buffer_size * 8);

    channels = get_bits(&alac->gb, 3);

    *outputsize = outputsamples * alac->bytespersample;

    switch(channels) {
    case 0: { /* 1 channel */
        int hassize;
        int isnotcompressed;
        int readsamplesize;

        int wasted_bytes;
        int ricemodifier;


        /* 2^result = something to do with output waiting.
         * perhaps matters if we read > 1 frame in a pass?
         */
        get_bits(&alac->gb, 4);

        get_bits(&alac->gb, 12); /* unknown, skip 12 bits */

        hassize = get_bits(&alac->gb, 1); /* the output sample size is stored soon */

        wasted_bytes = get_bits(&alac->gb, 2); /* unknown ? */

        isnotcompressed = get_bits(&alac->gb, 1); /* whether the frame is compressed */

        if (hassize) {
            /* now read the number of samples,
             * as a 32bit integer */
            outputsamples = get_bits(&alac->gb, 32);
            *outputsize = outputsamples * alac->bytespersample;
        }

        readsamplesize = alac->setinfo_sample_size - (wasted_bytes * 8);

        if (!isnotcompressed) {
         /* so it is compressed */
            int16_t predictor_coef_table[32];
            int predictor_coef_num;
            int prediction_type;
            int prediction_quantitization;
            int i;

            /* skip 16 bits, not sure what they are. seem to be used in
             * two channel case */
            get_bits(&alac->gb, 8);
            get_bits(&alac->gb, 8);

            prediction_type = get_bits(&alac->gb, 4);
            prediction_quantitization = get_bits(&alac->gb, 4);

            ricemodifier = get_bits(&alac->gb, 3);
            predictor_coef_num = get_bits(&alac->gb, 5);

            /* read the predictor table */
            for (i = 0; i < predictor_coef_num; i++) {
                predictor_coef_table[i] = (int16_t)get_bits(&alac->gb, 16);
            }

            if (wasted_bytes) {
                /* these bytes seem to have something to do with
                 * > 2 channel files.
                 */
                av_log(NULL, AV_LOG_ERROR, "FIXME: unimplemented, unhandling of wasted_bytes\n");
            }

            bastardized_rice_decompress(alac,
                                        alac->predicterror_buffer_a,
                                        outputsamples,
                                        readsamplesize,
                                        alac->setinfo_rice_initialhistory,
                                        alac->setinfo_rice_kmodifier,
                                        ricemodifier * alac->setinfo_rice_historymult / 4,
                                        (1 << alac->setinfo_rice_kmodifier) - 1);

            if (prediction_type == 0) {
              /* adaptive fir */
                predictor_decompress_fir_adapt(alac->predicterror_buffer_a,
                                               alac->outputsamples_buffer_a,
                                               outputsamples,
                                               readsamplesize,
                                               predictor_coef_table,
                                               predictor_coef_num,
                                               prediction_quantitization);
            } else {
                av_log(NULL, AV_LOG_ERROR, "FIXME: unhandled prediction type: %i\n", prediction_type);
                /* i think the only other prediction type (or perhaps this is just a
                 * boolean?) runs adaptive fir twice.. like:
                 * predictor_decompress_fir_adapt(predictor_error, tempout, ...)
                 * predictor_decompress_fir_adapt(predictor_error, outputsamples ...)
                 * little strange..
                 */
            }

        } else {
          /* not compressed, easy case */
            if (readsamplesize <= 16) {
                int i;
                for (i = 0; i < outputsamples; i++) {
                    int32_t audiobits = get_bits(&alac->gb, readsamplesize);

                    audiobits = SIGN_EXTENDED32(audiobits, readsamplesize);

                    alac->outputsamples_buffer_a[i] = audiobits;
                }
            } else {
                int i;
                for (i = 0; i < outputsamples; i++) {
                    int32_t audiobits;

                    audiobits = get_bits(&alac->gb, 16);
                    /* special case of sign extension..
                     * as we'll be ORing the low 16bits into this */
                    audiobits = audiobits << 16;
                    audiobits = audiobits >> (32 - readsamplesize);

                    audiobits |= get_bits(&alac->gb, readsamplesize - 16);

                    alac->outputsamples_buffer_a[i] = audiobits;
                }
            }
            /* wasted_bytes = 0; // unused */
        }

        switch(alac->setinfo_sample_size) {
        case 16: {
            int i;
            for (i = 0; i < outputsamples; i++) {
                int16_t sample = alac->outputsamples_buffer_a[i];
                sample = be2me_16(sample);
                ((int16_t*)outbuffer)[i * alac->numchannels] = sample;
            }
            break;
        }
        case 20:
        case 24:
        case 32:
            av_log(NULL, AV_LOG_ERROR, "FIXME: unimplemented sample size %i\n", alac->setinfo_sample_size);
            break;
        default:
            break;
        }
        break;
    }
    case 1: { /* 2 channels */
        int hassize;
        int isnotcompressed;
        int readsamplesize;

        int wasted_bytes;

        uint8_t interlacing_shift;
        uint8_t interlacing_leftweight;

        /* 2^result = something to do with output waiting.
         * perhaps matters if we read > 1 frame in a pass?
         */
        get_bits(&alac->gb, 4);

        get_bits(&alac->gb, 12); /* unknown, skip 12 bits */

        hassize = get_bits(&alac->gb, 1); /* the output sample size is stored soon */

        wasted_bytes = get_bits(&alac->gb, 2); /* unknown ? */

        isnotcompressed = get_bits(&alac->gb, 1); /* whether the frame is compressed */

        if (hassize) {
            /* now read the number of samples,
             * as a 32bit integer */
            outputsamples = get_bits(&alac->gb, 32);
            *outputsize = outputsamples * alac->bytespersample;
        }

        readsamplesize = alac->setinfo_sample_size - (wasted_bytes * 8) + 1;

        if (!isnotcompressed) {
         /* compressed */
            int16_t predictor_coef_table_a[32];
            int predictor_coef_num_a;
            int prediction_type_a;
            int prediction_quantitization_a;
            int ricemodifier_a;

            int16_t predictor_coef_table_b[32];
            int predictor_coef_num_b;
            int prediction_type_b;
            int prediction_quantitization_b;
            int ricemodifier_b;

            int i;

            interlacing_shift = get_bits(&alac->gb, 8);
            interlacing_leftweight = get_bits(&alac->gb, 8);

            /******** channel 1 ***********/
            prediction_type_a = get_bits(&alac->gb, 4);
            prediction_quantitization_a = get_bits(&alac->gb, 4);

            ricemodifier_a = get_bits(&alac->gb, 3);
            predictor_coef_num_a = get_bits(&alac->gb, 5);

            /* read the predictor table */
            for (i = 0; i < predictor_coef_num_a; i++) {
                predictor_coef_table_a[i] = (int16_t)get_bits(&alac->gb, 16);
            }

            /******** channel 2 *********/
            prediction_type_b = get_bits(&alac->gb, 4);
            prediction_quantitization_b = get_bits(&alac->gb, 4);

            ricemodifier_b = get_bits(&alac->gb, 3);
            predictor_coef_num_b = get_bits(&alac->gb, 5);

            /* read the predictor table */
            for (i = 0; i < predictor_coef_num_b; i++) {
                predictor_coef_table_b[i] = (int16_t)get_bits(&alac->gb, 16);
            }

            /*********************/
            if (wasted_bytes) {
              /* see mono case */
                av_log(NULL, AV_LOG_ERROR, "FIXME: unimplemented, unhandling of wasted_bytes\n");
            }

            /* channel 1 */
            bastardized_rice_decompress(alac,
                                        alac->predicterror_buffer_a,
                                        outputsamples,
                                        readsamplesize,
                                        alac->setinfo_rice_initialhistory,
                                        alac->setinfo_rice_kmodifier,
                                        ricemodifier_a * alac->setinfo_rice_historymult / 4,
                                        (1 << alac->setinfo_rice_kmodifier) - 1);

            if (prediction_type_a == 0) {
              /* adaptive fir */
                predictor_decompress_fir_adapt(alac->predicterror_buffer_a,
                                               alac->outputsamples_buffer_a,
                                               outputsamples,
                                               readsamplesize,
                                               predictor_coef_table_a,
                                               predictor_coef_num_a,
                                               prediction_quantitization_a);
            } else {
              /* see mono case */
                av_log(NULL, AV_LOG_ERROR, "FIXME: unhandled prediction type: %i\n", prediction_type_a);
            }

            /* channel 2 */
            bastardized_rice_decompress(alac,
                                        alac->predicterror_buffer_b,
                                        outputsamples,
                                        readsamplesize,
                                        alac->setinfo_rice_initialhistory,
                                        alac->setinfo_rice_kmodifier,
                                        ricemodifier_b * alac->setinfo_rice_historymult / 4,
                                        (1 << alac->setinfo_rice_kmodifier) - 1);

            if (prediction_type_b == 0) {
              /* adaptive fir */
                predictor_decompress_fir_adapt(alac->predicterror_buffer_b,
                                               alac->outputsamples_buffer_b,
                                               outputsamples,
                                               readsamplesize,
                                               predictor_coef_table_b,
                                               predictor_coef_num_b,
                                               prediction_quantitization_b);
            } else {
                av_log(NULL, AV_LOG_ERROR, "FIXME: unhandled prediction type: %i\n", prediction_type_b);
            }
        } else { 
         /* not compressed, easy case */
            if (alac->setinfo_sample_size <= 16) {
                int i;
                for (i = 0; i < outputsamples; i++) {
                    int32_t audiobits_a, audiobits_b;

                    audiobits_a = get_bits(&alac->gb, alac->setinfo_sample_size);
                    audiobits_b = get_bits(&alac->gb, alac->setinfo_sample_size);

                    audiobits_a = SIGN_EXTENDED32(audiobits_a, alac->setinfo_sample_size);
                    audiobits_b = SIGN_EXTENDED32(audiobits_b, alac->setinfo_sample_size);

                    alac->outputsamples_buffer_a[i] = audiobits_a;
                    alac->outputsamples_buffer_b[i] = audiobits_b;
                }
            } else {
                int i;
                for (i = 0; i < outputsamples; i++) {
                    int32_t audiobits_a, audiobits_b;

                    audiobits_a = get_bits(&alac->gb, 16);
                    audiobits_a = audiobits_a << 16;
                    audiobits_a = audiobits_a >> (32 - alac->setinfo_sample_size);
                    audiobits_a |= get_bits(&alac->gb, alac->setinfo_sample_size - 16);

                    audiobits_b = get_bits(&alac->gb, 16);
                    audiobits_b = audiobits_b << 16;
                    audiobits_b = audiobits_b >> (32 - alac->setinfo_sample_size);
                    audiobits_b |= get_bits(&alac->gb, alac->setinfo_sample_size - 16);

                    alac->outputsamples_buffer_a[i] = audiobits_a;
                    alac->outputsamples_buffer_b[i] = audiobits_b;
                }
            }
            /* wasted_bytes = 0; */
            interlacing_shift = 0;
            interlacing_leftweight = 0;
        }

        switch(alac->setinfo_sample_size) {
        case 16: {
            deinterlace_16(alac->outputsamples_buffer_a,
                           alac->outputsamples_buffer_b,
                           (int16_t*)outbuffer,
                           alac->numchannels,
                           outputsamples,
                           interlacing_shift,
                           interlacing_leftweight);
            break;
        }
        case 20:
        case 24:
        case 32:
            av_log(NULL, AV_LOG_ERROR, "FIXME: unimplemented sample size %i\n", alac->setinfo_sample_size);
            break;
        default:
            break;
        }

        break;
    }
    }

    return input_buffer_size;
}

static int alac_decode_init(AVCodecContext * avctx)
{
    ALACContext *alac = avctx->priv_data;
    alac->avctx = avctx;
    alac->context_initialized = 0;

    alac->samplesize = alac->avctx->bits_per_sample;
    alac->numchannels = alac->avctx->channels;
    alac->bytespersample = (alac->samplesize / 8) * alac->numchannels;

    return 0;
}

static int alac_decode_close(AVCodecContext *avctx)
{
    ALACContext *alac = avctx->priv_data;

    av_free(alac->predicterror_buffer_a);
    av_free(alac->predicterror_buffer_b);

    av_free(alac->outputsamples_buffer_a);
    av_free(alac->outputsamples_buffer_b);

    return 0;
}

AVCodec alac_decoder = {
    "alac",
    CODEC_TYPE_AUDIO,
    CODEC_ID_ALAC,
    sizeof(ALACContext),
    alac_decode_init,
    NULL,
    alac_decode_close,
    alac_decode_frame,
};