cook.c

ffmpeg源码分析

static void decouple_info(COOKContext *q, int* decouple_tab){
    int length, i;

    if(get_bits1(&q->gb)) {
        if(cplband[q->js_subband_start] > cplband[q->subbands-1]) return;

        length = cplband[q->subbands-1] - cplband[q->js_subband_start] + 1;
        for (i=0 ; i<length ; i++) {
            decouple_tab[cplband[q->js_subband_start] + i] = get_vlc2(&q->gb, q->ccpl.table, q->ccpl.bits, 2);
        }
        return;
    }

    if(cplband[q->js_subband_start] > cplband[q->subbands-1]) return;

    length = cplband[q->subbands-1] - cplband[q->js_subband_start] + 1;
    for (i=0 ; i<length ; i++) {
       decouple_tab[cplband[q->js_subband_start] + i] = get_bits(&q->gb, q->js_vlc_bits);
    }
    return;
}


/**
 * function for decoding joint stereo data
 *
 * @param q                 pointer to the COOKContext
 * @param mlt_buffer1       pointer to left channel mlt coefficients
 * @param mlt_buffer2       pointer to right channel mlt coefficients
 */

static void joint_decode(COOKContext *q, float* mlt_buffer1,
                         float* mlt_buffer2) {
    int i,j;
    int decouple_tab[SUBBAND_SIZE];
    float decode_buffer[1060];
    int idx, cpl_tmp,tmp_idx;
    float f1,f2;
    float* cplscale;

    memset(decouple_tab, 0, sizeof(decouple_tab));
    memset(decode_buffer, 0, sizeof(decode_buffer));

    /* Make sure the buffers are zeroed out. */
    memset(mlt_buffer1,0, 1024*sizeof(float));
    memset(mlt_buffer2,0, 1024*sizeof(float));
    decouple_info(q, decouple_tab);
    mono_decode(q, decode_buffer);

    /* The two channels are stored interleaved in decode_buffer. */
    for (i=0 ; i<q->js_subband_start ; i++) {
        for (j=0 ; j<SUBBAND_SIZE ; j++) {
            mlt_buffer1[i*20+j] = decode_buffer[i*40+j];
            mlt_buffer2[i*20+j] = decode_buffer[i*40+20+j];
        }
    }

    /* When we reach js_subband_start (the higher frequencies)
       the coefficients are stored in a coupling scheme. */
    idx = (1 << q->js_vlc_bits) - 1;
    for (i=q->js_subband_start ; i<q->subbands ; i++) {
        cpl_tmp = cplband[i];
        idx -=decouple_tab[cpl_tmp];
        cplscale = (float*)cplscales[q->js_vlc_bits-2];  //choose decoupler table
        f1 = cplscale[decouple_tab[cpl_tmp]];
        f2 = cplscale[idx-1];
        for (j=0 ; j<SUBBAND_SIZE ; j++) {
            tmp_idx = ((q->js_subband_start + i)*20)+j;
            mlt_buffer1[20*i + j] = f1 * decode_buffer[tmp_idx];
            mlt_buffer2[20*i + j] = f2 * decode_buffer[tmp_idx];
        }
        idx = (1 << q->js_vlc_bits) - 1;
    }
}

/**
 * Cook subpacket decoding. This function returns one decoded subpacket,
 * usually 1024 samples per channel.
 *
 * @param q                 pointer to the COOKContext
 * @param inbuffer          pointer to the inbuffer
 * @param sub_packet_size   subpacket size
 * @param outbuffer         pointer to the outbuffer
 */


static int decode_subpacket(COOKContext *q, uint8_t *inbuffer,
                            int sub_packet_size, int16_t *outbuffer) {
    int i,j;
    int value;
    float* tmp_ptr;

    /* packet dump */
//    for (i=0 ; i<sub_packet_size ; i++) {
//        av_log(NULL, AV_LOG_ERROR, "%02x", inbuffer[i]);
//    }
//    av_log(NULL, AV_LOG_ERROR, "\n");

    decode_bytes(inbuffer, q->decoded_bytes_buffer, sub_packet_size);
    init_get_bits(&q->gb, q->decoded_bytes_buffer, sub_packet_size*8);
    decode_gain_info(&q->gb, &q->gain_current);

    if(q->nb_channels==2 && q->joint_stereo==1){
        joint_decode(q, q->decode_buf_ptr[0], q->decode_buf_ptr[2]);

        /* Swap buffer pointers. */
        tmp_ptr = q->decode_buf_ptr[1];
        q->decode_buf_ptr[1] = q->decode_buf_ptr[0];
        q->decode_buf_ptr[0] = tmp_ptr;
        tmp_ptr = q->decode_buf_ptr[3];
        q->decode_buf_ptr[3] = q->decode_buf_ptr[2];
        q->decode_buf_ptr[2] = tmp_ptr;

        /* FIXME: Rethink the gainbuffer handling, maybe a rename?
           now/previous swap */
        q->gain_now_ptr = &q->gain_now;
        q->gain_previous_ptr = &q->gain_previous;
        for (i=0 ; i<q->nb_channels ; i++){

            cook_imlt(q, q->decode_buf_ptr[i*2], q->mono_mdct_output, q->mlt_tmp);
            gain_compensate(q, q->mono_mdct_output, q->gain_now_ptr,
                            q->gain_previous_ptr, q->previous_buffer_ptr[0]);

            /* Swap out the previous buffer. */
            tmp_ptr = q->previous_buffer_ptr[0];
            q->previous_buffer_ptr[0] = q->previous_buffer_ptr[1];
            q->previous_buffer_ptr[1] = tmp_ptr;

            /* Clip and convert the floats to 16 bits. */
            for (j=0 ; j<q->samples_per_frame ; j++){
                value = lrintf(q->mono_mdct_output[j]);
                if(value < -32768) value = -32768;
                else if(value > 32767) value = 32767;
                outbuffer[2*j+i] = value;
            }
        }

        memcpy(&q->gain_now, &q->gain_previous, sizeof(COOKgain));
        memcpy(&q->gain_previous, &q->gain_current, sizeof(COOKgain));

    } else if (q->nb_channels==2 && q->joint_stereo==0) {
            /* channel 0 */
            mono_decode(q, q->decode_buf_ptr2[0]);

            tmp_ptr = q->decode_buf_ptr2[0];
            q->decode_buf_ptr2[0] = q->decode_buf_ptr2[1];
            q->decode_buf_ptr2[1] = tmp_ptr;

            memcpy(&q->gain_channel1[0], &q->gain_current ,sizeof(COOKgain));
            q->gain_now_ptr = &q->gain_channel1[0];
            q->gain_previous_ptr = &q->gain_channel1[1];

            cook_imlt(q, q->decode_buf_ptr2[0], q->mono_mdct_output,q->mlt_tmp);
            gain_compensate(q, q->mono_mdct_output, q->gain_now_ptr,
                            q->gain_previous_ptr, q->mono_previous_buffer1);

            memcpy(&q->gain_channel1[1], &q->gain_channel1[0],sizeof(COOKgain));


            for (j=0 ; j<q->samples_per_frame ; j++){
                value = lrintf(q->mono_mdct_output[j]);
                if(value < -32768) value = -32768;
                else if(value > 32767) value = 32767;
                outbuffer[2*j+1] = value;
            }

            /* channel 1 */
            //av_log(NULL,AV_LOG_ERROR,"bits = %d\n",get_bits_count(&q->gb));
            init_get_bits(&q->gb, q->decoded_bytes_buffer, sub_packet_size*8+q->bits_per_subpacket);

            q->gain_now_ptr = &q->gain_channel2[0];
            q->gain_previous_ptr = &q->gain_channel2[1];

            decode_gain_info(&q->gb, &q->gain_channel2[0]);
            mono_decode(q, q->decode_buf_ptr[0]);

            tmp_ptr = q->decode_buf_ptr[0];
            q->decode_buf_ptr[0] = q->decode_buf_ptr[1];
            q->decode_buf_ptr[1] = tmp_ptr;

            cook_imlt(q, q->decode_buf_ptr[0], q->mono_mdct_output,q->mlt_tmp);
            gain_compensate(q, q->mono_mdct_output, q->gain_now_ptr,
                            q->gain_previous_ptr, q->mono_previous_buffer2);

            /* Swap out the previous buffer. */
            tmp_ptr = q->previous_buffer_ptr[0];
            q->previous_buffer_ptr[0] = q->previous_buffer_ptr[1];
            q->previous_buffer_ptr[1] = tmp_ptr;

            memcpy(&q->gain_channel2[1], &q->gain_channel2[0] ,sizeof(COOKgain));

            for (j=0 ; j<q->samples_per_frame ; j++){
                value = lrintf(q->mono_mdct_output[j]);
                if(value < -32768) value = -32768;
                else if(value > 32767) value = 32767;
                outbuffer[2*j] = value;
            }

    } else {
        mono_decode(q, q->decode_buf_ptr[0]);

        /* Swap buffer pointers. */
        tmp_ptr = q->decode_buf_ptr[1];
        q->decode_buf_ptr[1] = q->decode_buf_ptr[0];
        q->decode_buf_ptr[0] = tmp_ptr;

        /* FIXME: Rethink the gainbuffer handling, maybe a rename?
           now/previous swap */
        q->gain_now_ptr = &q->gain_now;
        q->gain_previous_ptr = &q->gain_previous;

        cook_imlt(q, q->decode_buf_ptr[0], q->mono_mdct_output,q->mlt_tmp);
        gain_compensate(q, q->mono_mdct_output, q->gain_now_ptr,
                        q->gain_previous_ptr, q->mono_previous_buffer1);

        /* Clip and convert the floats to 16 bits */
        for (j=0 ; j<q->samples_per_frame ; j++){
            value = lrintf(q->mono_mdct_output[j]);
            if(value < -32768) value = -32768;
            else if(value > 32767) value = 32767;
            outbuffer[j] = value;
        }
        memcpy(&q->gain_now, &q->gain_previous, sizeof(COOKgain));
        memcpy(&q->gain_previous, &q->gain_current, sizeof(COOKgain));
    }
    return q->samples_per_frame * sizeof(int16_t);
}


/**
 * Cook frame decoding
 *
 * @param avctx     pointer to the AVCodecContext
 */

static int cook_decode_frame(AVCodecContext *avctx,
            void *data, int *data_size,
            uint8_t *buf, int buf_size) {
    COOKContext *q = avctx->priv_data;

    if (buf_size < avctx->block_align)
        return buf_size;

    *data_size = decode_subpacket(q, buf, avctx->block_align, data);

    return avctx->block_align;
}

#ifdef COOKDEBUG
static void dump_cook_context(COOKContext *q, COOKextradata *e)
{
    //int i=0;
#define PRINT(a,b) av_log(NULL,AV_LOG_ERROR," %s = %d\n", a, b);
    av_log(NULL,AV_LOG_ERROR,"COOKextradata\n");
    av_log(NULL,AV_LOG_ERROR,"cookversion=%x\n",e->cookversion);
    if (e->cookversion > MONO_COOK2) {
        PRINT("js_subband_start",e->js_subband_start);
        PRINT("js_vlc_bits",e->js_vlc_bits);
    }
    av_log(NULL,AV_LOG_ERROR,"COOKContext\n");
    PRINT("nb_channels",q->nb_channels);
    PRINT("bit_rate",q->bit_rate);
    PRINT("sample_rate",q->sample_rate);
    PRINT("samples_per_channel",q->samples_per_channel);
    PRINT("samples_per_frame",q->samples_per_frame);
    PRINT("subbands",q->subbands);
    PRINT("random_state",q->random_state);
    PRINT("mlt_size",q->mlt_size);
    PRINT("js_subband_start",q->js_subband_start);
    PRINT("log2_numvector_size",q->log2_numvector_size);
    PRINT("numvector_size",q->numvector_size);
    PRINT("total_subbands",q->total_subbands);
}
#endif

/**
 * Cook initialization
 *
 * @param avctx     pointer to the AVCodecContext
 */

static int cook_decode_init(AVCodecContext *avctx)
{
    COOKextradata *e = avctx->extradata;
    COOKContext *q = avctx->priv_data;

    /* Take care of the codec specific extradata. */
    if (avctx->extradata_size <= 0) {
        av_log(NULL,AV_LOG_ERROR,"Necessary extradata missing!\n");
        return -1;
    } else {
        /* 8 for mono, 16 for stereo, ? for multichannel
           Swap to right endianness so we don't need to care later on. */
        av_log(NULL,AV_LOG_DEBUG,"codecdata_length=%d\n",avctx->extradata_size);
        if (avctx->extradata_size >= 8){
            e->cookversion = be2me_32(e->cookversion);
            e->samples_per_frame = be2me_16(e->samples_per_frame);
            e->subbands = be2me_16(e->subbands);
        }
        if (avctx->extradata_size >= 16){
            e->js_subband_start = be2me_16(e->js_subband_start);
            e->js_vlc_bits = be2me_16(e->js_vlc_bits);
        }
    }

    /* Take data from the AVCodecContext (RM container). */
    q->sample_rate = avctx->sample_rate;
    q->nb_channels = avctx->channels;
    q->bit_rate = avctx->bit_rate;

    /* Initialize state. */
    q->random_state = 1;

    /* Initialize extradata related variables. */
    q->samples_per_channel = e->samples_per_frame / q->nb_channels;
    q->samples_per_frame = e->samples_per_frame;
    q->subbands = e->subbands;
    q->bits_per_subpacket = avctx->block_align * 8;

    /* Initialize default data states. */
    q->js_subband_start = 0;
    q->log2_numvector_size = 5;
    q->total_subbands = q->subbands;

    /* Initialize version-dependent variables */
    av_log(NULL,AV_LOG_DEBUG,"e->cookversion=%x\n",e->cookversion);
    switch (e->cookversion) {
        case MONO_COOK1:
            if (q->nb_channels != 1) {
                av_log(NULL,AV_LOG_ERROR,"Container channels != 1, report sample!\n");
                return -1;
            }
            av_log(NULL,AV_LOG_DEBUG,"MONO_COOK1\n");
            break;
        case MONO_COOK2:
            if (q->nb_channels != 1) {
                q->joint_stereo = 0;
                q->bits_per_subpacket = q->bits_per_subpacket/2;
            }
            av_log(NULL,AV_LOG_DEBUG,"MONO_COOK2\n");
            break;
        case JOINT_STEREO:
            if (q->nb_channels != 2) {
                av_log(NULL,AV_LOG_ERROR,"Container channels != 2, report sample!\n");
                return -1;
            }
            av_log(NULL,AV_LOG_DEBUG,"JOINT_STEREO\n");
            if (avctx->extradata_size >= 16){
                q->total_subbands = q->subbands + e->js_subband_start;
                q->js_subband_start = e->js_subband_start;
                q->joint_stereo = 1;
                q->js_vlc_bits = e->js_vlc_bits;
            }
            if (q->samples_per_channel > 256) {
                q->log2_numvector_size  = 6;
            }
            if (q->samples_per_channel > 512) {
                q->log2_numvector_size  = 7;
            }
            break;
        case MC_COOK:
            av_log(NULL,AV_LOG_ERROR,"MC_COOK not supported!\n");
            return -1;
            break;
        default:
            av_log(NULL,AV_LOG_ERROR,"Unknown Cook version, report sample!\n");
            return -1;
            break;
    }

    /* Initialize variable relations */
    q->mlt_size = q->samples_per_channel;
    q->numvector_size = (1 << q->log2_numvector_size);

    /* Generate tables */
    init_rootpow2table(q);
    init_pow2table(q);
    init_gain_table(q);

    if (init_cook_vlc_tables(q) != 0)
        return -1;

    /* Pad the databuffer with FF_INPUT_BUFFER_PADDING_SIZE,
       this is for the bitstreamreader. */
    if ((q->decoded_bytes_buffer = av_mallocz((avctx->block_align+(4-avctx->block_align%4) + FF_INPUT_BUFFER_PADDING_SIZE)*sizeof(uint8_t)))  == NULL)
        return -1;

    q->decode_buf_ptr[0] = q->decode_buffer_1;
    q->decode_buf_ptr[1] = q->decode_buffer_2;
    q->decode_buf_ptr[2] = q->decode_buffer_3;
    q->decode_buf_ptr[3] = q->decode_buffer_4;

    q->decode_buf_ptr2[0] = q->decode_buffer_3;
    q->decode_buf_ptr2[1] = q->decode_buffer_4;

    q->previous_buffer_ptr[0] = q->mono_previous_buffer1;
    q->previous_buffer_ptr[1] = q->mono_previous_buffer2;

    /* Initialize transform. */
    if ( init_cook_mlt(q) == 0 )
        return -1;

    /* Try to catch some obviously faulty streams, othervise it might be exploitable */
    if (q->total_subbands > 53) {
        av_log(NULL,AV_LOG_ERROR,"total_subbands > 53, report sample!\n");
        return -1;
    }
    if (q->subbands > 50) {
        av_log(NULL,AV_LOG_ERROR,"subbands > 50, report sample!\n");
        return -1;
    }
    if ((q->samples_per_channel == 256) || (q->samples_per_channel == 512) || (q->samples_per_channel == 1024)) {
    } else {
        av_log(NULL,AV_LOG_ERROR,"unknown amount of samples_per_channel = %d, report sample!\n",q->samples_per_channel);
        return -1;
    }

#ifdef COOKDEBUG
    dump_cook_context(q,e);
#endif
    return 0;
}


AVCodec cook_decoder =
{
    .name = "cook",
    .type = CODEC_TYPE_AUDIO,
    .id = CODEC_ID_COOK,
    .priv_data_size = sizeof(COOKContext),
    .init = cook_decode_init,
    .close = cook_decode_close,
    .decode = cook_decode_frame,
};