func: static int pcm_decode_frame(AVCodecContext *avctx,
                              void *data, int *data_size,
                              AVPacket *avpkt)
  {
      const uint8_t *buf = avpkt->data;
      int buf_size = avpkt->size;
      PCMDecode *s = avctx->priv_data;
      int sample_size, c, n, i;
      short *samples;
      const uint8_t *src, *src8, *src2[MAX_CHANNELS];
      uint8_t *dstu8;
      int16_t *dst_int16_t;
      int32_t *dst_int32_t;
      int64_t *dst_int64_t;
      uint16_t *dst_uint16_t;
      uint32_t *dst_uint32_t;
      samples = data;
      src = buf;
      if (avctx->sample_fmt!=avctx->codec->sample_fmts[0]) {
          av_log(avctx, AV_LOG_ERROR, "invalid sample_fmt\n");
          return -1;
      if(avctx->channels <= 0 || avctx->channels > MAX_CHANNELS){
          av_log(avctx, AV_LOG_ERROR, "PCM channels out of bounds\n");
          return -1;
      sample_size = av_get_bits_per_sample(avctx->codec_id)/8;
      /* av_get_bits_per_sample returns 0 for CODEC_ID_PCM_DVD */
      if (CODEC_ID_PCM_DVD == avctx->codec_id)
          /* 2 samples are interleaved per block in PCM_DVD */
          sample_size = avctx->bits_per_coded_sample * 2 / 8;
      else if (avctx->codec_id == CODEC_ID_PCM_LXF)
          /* we process 40-bit blocks per channel for LXF */
          sample_size = 5;
      n = avctx->channels * sample_size;
      if(n && buf_size % n){
          if (buf_size < n) {
              av_log(avctx, AV_LOG_ERROR, "invalid PCM packet\n");
              return -1;
          }else
              buf_size -= buf_size % n;
      buf_size= FFMIN(buf_size, *data_size/2);
      *data_size=0;
      n = buf_size/sample_size;
      switch(avctx->codec->id) {
      case CODEC_ID_PCM_U32LE:
          DECODE(uint32_t, le32, src, samples, n, 0, 0x80000000)
          break;
      case CODEC_ID_PCM_U32BE:
          DECODE(uint32_t, be32, src, samples, n, 0, 0x80000000)
          break;
      case CODEC_ID_PCM_S24LE:
          DECODE(int32_t, le24, src, samples, n, 8, 0)
          break;
      case CODEC_ID_PCM_S24BE:
          DECODE(int32_t, be24, src, samples, n, 8, 0)
          break;
      case CODEC_ID_PCM_U24LE:
          DECODE(uint32_t, le24, src, samples, n, 8, 0x800000)
          break;
      case CODEC_ID_PCM_U24BE:
          DECODE(uint32_t, be24, src, samples, n, 8, 0x800000)
          break;
      case CODEC_ID_PCM_S24DAUD:
          for(;n>0;n--) {
            uint32_t v = bytestream_get_be24(&src);
            v >>= 4; // sync flags are here
            *samples++ = av_reverse[(v >> 8) & 0xff] +
                         (av_reverse[v & 0xff] << 8);
          break;
      case CODEC_ID_PCM_S16LE_PLANAR:
          n /= avctx->channels;
          for(c=0;c<avctx->channels;c++)
              src2[c] = &src[c*n*2];
          for(;n>0;n--)
              for(c=0;c<avctx->channels;c++)
                  *samples++ = bytestream_get_le16(&src2[c]);
          src = src2[avctx->channels-1];
          break;
      case CODEC_ID_PCM_U16LE:
          DECODE(uint16_t, le16, src, samples, n, 0, 0x8000)
          break;
      case CODEC_ID_PCM_U16BE:
          DECODE(uint16_t, be16, src, samples, n, 0, 0x8000)
          break;
      case CODEC_ID_PCM_S8:
          dstu8= (uint8_t*)samples;
          for(;n>0;n--) {
              *dstu8++ = *src++ + 128;
          samples= (short*)dstu8;
          break;
  #if HAVE_BIGENDIAN
      case CODEC_ID_PCM_F64LE:
          DECODE(int64_t, le64, src, samples, n, 0, 0)
          break;
      case CODEC_ID_PCM_S32LE:
      case CODEC_ID_PCM_F32LE:
          DECODE(int32_t, le32, src, samples, n, 0, 0)
          break;
      case CODEC_ID_PCM_S16LE:
          DECODE(int16_t, le16, src, samples, n, 0, 0)
          break;
      case CODEC_ID_PCM_F64BE:
      case CODEC_ID_PCM_F32BE:
      case CODEC_ID_PCM_S32BE:
      case CODEC_ID_PCM_S16BE:
  #else
      case CODEC_ID_PCM_F64BE:
          DECODE(int64_t, be64, src, samples, n, 0, 0)
          break;
      case CODEC_ID_PCM_F32BE:
      case CODEC_ID_PCM_S32BE:
          DECODE(int32_t, be32, src, samples, n, 0, 0)
          break;
      case CODEC_ID_PCM_S16BE:
          DECODE(int16_t, be16, src, samples, n, 0, 0)
          break;
      case CODEC_ID_PCM_F64LE:
      case CODEC_ID_PCM_F32LE:
      case CODEC_ID_PCM_S32LE:
      case CODEC_ID_PCM_S16LE:
  #endif /* HAVE_BIGENDIAN */
      case CODEC_ID_PCM_U8:
          memcpy(samples, src, n*sample_size);
          src += n*sample_size;
          samples = (short*)((uint8_t*)data + n*sample_size);
          break;
      case CODEC_ID_PCM_ZORK:
          for(;n>0;n--) {
              int x= *src++;
              if(x&128) x-= 128;
              else      x = -x;
              *samples++ = x << 8;
          break;
      case CODEC_ID_PCM_ALAW:
      case CODEC_ID_PCM_MULAW:
          for(;n>0;n--) {
              *samples++ = s->table[*src++];
          break;
      case CODEC_ID_PCM_DVD:
          dst_int32_t = data;
          n /= avctx->channels;
          switch (avctx->bits_per_coded_sample) {
          case 20:
              while (n--) {
                  c = avctx->channels;
                  src8 = src + 4*c;
                  while (c--) {
                      *dst_int32_t++ = (bytestream_get_be16(&src) << 16) + ((*src8   &0xf0) << 8);
                      *dst_int32_t++ = (bytestream_get_be16(&src) << 16) + ((*src8++ &0x0f) << 12);
                  src = src8;
              break;
          case 24:
              while (n--) {
                  c = avctx->channels;
                  src8 = src + 4*c;
                  while (c--) {
                      *dst_int32_t++ = (bytestream_get_be16(&src) << 16) + ((*src8++) << 8);
                      *dst_int32_t++ = (bytestream_get_be16(&src) << 16) + ((*src8++) << 8);
                  src = src8;
              break;
          default:
              av_log(avctx, AV_LOG_ERROR, "PCM DVD unsupported sample depth\n");
              return -1;
              break;
          samples = (short *) dst_int32_t;
          break;
      case CODEC_ID_PCM_LXF:
          dst_int32_t = data;
          n /= avctx->channels;
          //unpack and de-planerize
          for (i = 0; i < n; i++) {
              for (c = 0, src8 = src + i*5; c < avctx->channels; c++, src8 += n*5) {
                  //extract low 20 bits and expand to 32 bits
                  *dst_int32_t++ = (src8[2] << 28) | (src8[1] << 20) | (src8[0] << 12) |
                                   ((src8[2] & 0xF) << 8) | src8[1];
              for (c = 0, src8 = src + i*5; c < avctx->channels; c++, src8 += n*5) {
                  //extract high 20 bits and expand to 32 bits
                  *dst_int32_t++ = (src8[4] << 24) | (src8[3] << 16) |
                                   ((src8[2] & 0xF0) << 8) | (src8[4] << 4) | (src8[3] >> 4);
          src += n * avctx->channels * 5;
          samples = (short *) dst_int32_t;
          break;
      default:
          return -1;
      *data_size = (uint8_t *)samples - (uint8_t *)data;
      return src - buf;