/*
  * Shorten decoder
  * Copyright (c) 2005 Jeff Muizelaar
  *

  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or

  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either

  * version 2.1 of the License, or (at your option) any later version.

  *

  * FFmpeg is distributed in the hope that it will be useful,

  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public

  * License along with FFmpeg; if not, write to the Free Software

  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

  */
 
 /**

  * @file

  * Shorten decoder
  * @author Jeff Muizelaar
  */
 
 #include <limits.h>
 #include "avcodec.h"

 #include "bswapdsp.h"

 #include "bytestream.h"

 #include "get_bits.h"

 #include "golomb.h"

 #include "internal.h"

 
 #define MAX_CHANNELS 8
 #define MAX_BLOCKSIZE 65535
 
 #define OUT_BUFFER_SIZE 16384
 
 #define ULONGSIZE 2
 
 #define WAVE_FORMAT_PCM 0x0001
 
 #define DEFAULT_BLOCK_SIZE 256
 
 #define TYPESIZE 4
 #define CHANSIZE 0
 #define LPCQSIZE 2
 #define ENERGYSIZE 3
 #define BITSHIFTSIZE 2
 

 #define TYPE_S8    1
 #define TYPE_U8    2

 #define TYPE_S16HL 3

 #define TYPE_U16HL 4

 #define TYPE_S16LH 5

 #define TYPE_U16LH 6

 
 #define NWRAP 3
 #define NSKIPSIZE 1
 
 #define LPCQUANT 5
 #define V2LPCQOFFSET (1 << LPCQUANT)
 
 #define FNSIZE 2
 #define FN_DIFF0        0
 #define FN_DIFF1        1
 #define FN_DIFF2        2
 #define FN_DIFF3        3
 #define FN_QUIT         4
 #define FN_BLOCKSIZE    5
 #define FN_BITSHIFT     6
 #define FN_QLPC         7
 #define FN_ZERO         8
 #define FN_VERBATIM     9
 

 /** indicates if the FN_* command is audio or non-audio */
 static const uint8_t is_audio_command[10] = { 1, 1, 1, 1, 0, 0, 0, 1, 1, 0 };
 

 #define VERBATIM_CKSIZE_SIZE 5
 #define VERBATIM_BYTE_SIZE 8
 #define CANONICAL_HEADER_SIZE 44
 
 typedef struct ShortenContext {
     AVCodecContext *avctx;
     GetBitContext gb;
 
     int min_framesize, max_framesize;

     unsigned channels;

 
     int32_t *decoded[MAX_CHANNELS];

     int32_t *decoded_base[MAX_CHANNELS];

     int32_t *offset[MAX_CHANNELS];

     int *coeffs;

     uint8_t *bitstream;
     int bitstream_size;
     int bitstream_index;

     unsigned int allocated_bitstream_size;

     int header_size;
     uint8_t header[OUT_BUFFER_SIZE];
     int version;
     int cur_chan;
     int bitshift;
     int nmean;
     int internal_ftype;
     int nwrap;
     int blocksize;
     int bitindex;
     int32_t lpcqoffset;

     int got_header;

     int got_quit_command;

     int swap;
     BswapDSPContext bdsp;

 } ShortenContext;
 

 static av_cold int shorten_decode_init(AVCodecContext *avctx)

 {
     ShortenContext *s = avctx->priv_data;

     s->avctx          = avctx;

     ff_bswapdsp_init(&s->bdsp);
 

     return 0;
 }
 

 static int allocate_buffers(ShortenContext *s)

 {

     int i, chan, err;

     for (chan = 0; chan < s->channels; chan++) {
         if (FFMAX(1, s->nmean) >= UINT_MAX / sizeof(int32_t)) {

             av_log(s->avctx, AV_LOG_ERROR, "nmean too large\n");

             return AVERROR_INVALIDDATA;

         }

         if (s->blocksize + (uint64_t)s->nwrap >= UINT_MAX / sizeof(int32_t)) {

             av_log(s->avctx, AV_LOG_ERROR,
                    "s->blocksize + s->nwrap too large\n");

             return AVERROR_INVALIDDATA;

         }
 

         if ((err = av_reallocp_array(&s->offset[chan],
                                sizeof(int32_t),

                                FFMAX(1, s->nmean))) < 0)
             return err;
 

         if ((err = av_reallocp_array(&s->decoded_base[chan], (s->blocksize + s->nwrap),

                                sizeof(s->decoded_base[0][0]))) < 0)
             return err;

         for (i = 0; i < s->nwrap; i++)

             s->decoded_base[chan][i] = 0;
         s->decoded[chan] = s->decoded_base[chan] + s->nwrap;

     }

     if ((err = av_reallocp_array(&s->coeffs, s->nwrap, sizeof(*s->coeffs))) < 0)

         return err;

     return 0;

 }
 
 static inline unsigned int get_uint(ShortenContext *s, int k)
 {

     if (s->version != 0) {

         k = get_ur_golomb_shorten(&s->gb, ULONGSIZE);

         if (k > 31U)
             return AVERROR_INVALIDDATA;
     }

     return get_ur_golomb_shorten(&s->gb, k);
 }
 
 static void fix_bitshift(ShortenContext *s, int32_t *buffer)
 {
     int i;
 

     if (s->bitshift == 32) {
         for (i = 0; i < s->blocksize; i++)
             buffer[i] = 0;
     } else if (s->bitshift != 0) {

         for (i = 0; i < s->blocksize; i++)

             buffer[i] *= 1U << s->bitshift;

     }

 }
 

 static int init_offset(ShortenContext *s)

 {
     int32_t mean = 0;

     int chan, i;

     int nblock = FFMAX(1, s->nmean);
     /* initialise offset */

     switch (s->internal_ftype) {

     case TYPE_U8:
         s->avctx->sample_fmt = AV_SAMPLE_FMT_U8P;
         mean = 0x80;
         break;

     case TYPE_S16HL:
     case TYPE_S16LH:

         s->avctx->sample_fmt = AV_SAMPLE_FMT_S16P;

         break;
     default:

         av_log(s->avctx, AV_LOG_ERROR, "unknown audio type\n");
         return AVERROR_PATCHWELCOME;

     }
 
     for (chan = 0; chan < s->channels; chan++)
         for (i = 0; i < nblock; i++)
             s->offset[chan][i] = mean;

     return 0;

 }
 

 static int decode_aiff_header(AVCodecContext *avctx, const uint8_t *header,
                               int header_size)
 {

     ShortenContext *s = avctx->priv_data;

     int len, bps, exp;
     GetByteContext gb;
     uint64_t val;
     uint32_t tag;
 
     bytestream2_init(&gb, header, header_size);
 
     if (bytestream2_get_le32(&gb) != MKTAG('F', 'O', 'R', 'M')) {
         av_log(avctx, AV_LOG_ERROR, "missing FORM tag\n");
         return AVERROR_INVALIDDATA;
     }
 
     bytestream2_skip(&gb, 4); /* chunk size */
 
     tag = bytestream2_get_le32(&gb);

     if (tag != MKTAG('A', 'I', 'F', 'F') &&
         tag != MKTAG('A', 'I', 'F', 'C')) {

         av_log(avctx, AV_LOG_ERROR, "missing AIFF tag\n");
         return AVERROR_INVALIDDATA;
     }
 
     while (bytestream2_get_le32(&gb) != MKTAG('C', 'O', 'M', 'M')) {
         len = bytestream2_get_be32(&gb);

         if (len < 0 || bytestream2_get_bytes_left(&gb) < 18LL + len + (len&1)) {

             av_log(avctx, AV_LOG_ERROR, "no COMM chunk found\n");
             return AVERROR_INVALIDDATA;
         }

         bytestream2_skip(&gb, len + (len & 1));

     }
     len = bytestream2_get_be32(&gb);
 
     if (len < 18) {
         av_log(avctx, AV_LOG_ERROR, "COMM chunk was too short\n");
         return AVERROR_INVALIDDATA;
     }
 
     bytestream2_skip(&gb, 6);
     bps = bytestream2_get_be16(&gb);
     avctx->bits_per_coded_sample = bps;
 

     s->swap = tag == MKTAG('A', 'I', 'F', 'C');
 

     if (bps != 16 && bps != 8) {
         av_log(avctx, AV_LOG_ERROR, "unsupported number of bits per sample: %d\n", bps);
         return AVERROR(ENOSYS);
     }
 
     exp = bytestream2_get_be16(&gb) - 16383 - 63;
     val = bytestream2_get_be64(&gb);
     if (exp < -63 || exp > 63) {
         av_log(avctx, AV_LOG_ERROR, "exp %d is out of range\n", exp);
         return AVERROR_INVALIDDATA;
     }
     if (exp >= 0)
         avctx->sample_rate = val << exp;
     else
         avctx->sample_rate = (val + (1ULL<<(-exp-1))) >> -exp;
     len -= 18;
     if (len > 0)
         av_log(avctx, AV_LOG_INFO, "%d header bytes unparsed\n", len);
 
     return 0;
 }
 

 static int decode_wave_header(AVCodecContext *avctx, const uint8_t *header,
                               int header_size)

 {

     int len, bps;

     short wave_format;

     GetByteContext gb;

     bytestream2_init(&gb, header, header_size);
 
     if (bytestream2_get_le32(&gb) != MKTAG('R', 'I', 'F', 'F')) {

         av_log(avctx, AV_LOG_ERROR, "missing RIFF tag\n");

         return AVERROR_INVALIDDATA;

     }
 

     bytestream2_skip(&gb, 4); /* chunk size */

     if (bytestream2_get_le32(&gb) != MKTAG('W', 'A', 'V', 'E')) {

         av_log(avctx, AV_LOG_ERROR, "missing WAVE tag\n");

         return AVERROR_INVALIDDATA;

     }
 

     while (bytestream2_get_le32(&gb) != MKTAG('f', 'm', 't', ' ')) {
         len = bytestream2_get_le32(&gb);
         bytestream2_skip(&gb, len);

         if (len < 0 || bytestream2_get_bytes_left(&gb) < 16) {

             av_log(avctx, AV_LOG_ERROR, "no fmt chunk found\n");
             return AVERROR_INVALIDDATA;
         }

     }

     len = bytestream2_get_le32(&gb);

 
     if (len < 16) {
         av_log(avctx, AV_LOG_ERROR, "fmt chunk was too short\n");

         return AVERROR_INVALIDDATA;

     }
 

     wave_format = bytestream2_get_le16(&gb);

 
     switch (wave_format) {

     case WAVE_FORMAT_PCM:
         break;
     default:
         av_log(avctx, AV_LOG_ERROR, "unsupported wave format\n");

         return AVERROR(ENOSYS);

     }
 

     bytestream2_skip(&gb, 2); // skip channels    (already got from shorten header)
     avctx->sample_rate = bytestream2_get_le32(&gb);
     bytestream2_skip(&gb, 4); // skip bit rate    (represents original uncompressed bit rate)
     bytestream2_skip(&gb, 2); // skip block align (not needed)

     bps = bytestream2_get_le16(&gb);

     avctx->bits_per_coded_sample = bps;

     if (bps != 16 && bps != 8) {
         av_log(avctx, AV_LOG_ERROR, "unsupported number of bits per sample: %d\n", bps);

         return AVERROR(ENOSYS);

     }
 
     len -= 16;
     if (len > 0)
         av_log(avctx, AV_LOG_INFO, "%d header bytes unparsed\n", len);
 
     return 0;
 }
 

 static const int fixed_coeffs[][3] = {
     { 0,  0,  0 },

     { 1,  0,  0 },
     { 2, -1,  0 },
     { 3, -3,  1 }
 };
 
 static int decode_subframe_lpc(ShortenContext *s, int command, int channel,

                                int residual_size, int32_t coffset)

 {

     int pred_order, sum, qshift, init_sum, i, j;
     const int *coeffs;
 
     if (command == FN_QLPC) {
         /* read/validate prediction order */
         pred_order = get_ur_golomb_shorten(&s->gb, LPCQSIZE);

         if ((unsigned)pred_order > s->nwrap) {

             av_log(s->avctx, AV_LOG_ERROR, "invalid pred_order %d\n",
                    pred_order);

             return AVERROR(EINVAL);
         }
         /* read LPC coefficients */

         for (i = 0; i < pred_order; i++)

             s->coeffs[i] = get_sr_golomb_shorten(&s->gb, LPCQUANT);
         coeffs = s->coeffs;
 
         qshift = LPCQUANT;
     } else {
         /* fixed LPC coeffs */
         pred_order = command;

         if (pred_order >= FF_ARRAY_ELEMS(fixed_coeffs)) {

             av_log(s->avctx, AV_LOG_ERROR, "invalid pred_order %d\n",
                    pred_order);
             return AVERROR_INVALIDDATA;
         }
         coeffs     = fixed_coeffs[pred_order];

         qshift     = 0;

     }

     /* subtract offset from previous samples to use in prediction */

     if (command == FN_QLPC && coffset)

         for (i = -pred_order; i < 0; i++)

             s->decoded[channel][i] -= (unsigned)coffset;

     /* decode residual and do LPC prediction */

     init_sum = pred_order ? (command == FN_QLPC ? s->lpcqoffset : 0) : coffset;

     for (i = 0; i < s->blocksize; i++) {

         sum = init_sum;

         for (j = 0; j < pred_order; j++)

             sum += coeffs[j] * (unsigned)s->decoded[channel][i - j - 1];

         s->decoded[channel][i] = get_sr_golomb_shorten(&s->gb, residual_size) +

                                  (unsigned)(sum >> qshift);

     }

 
     /* add offset to current samples */

     if (command == FN_QLPC && coffset)

         for (i = 0; i < s->blocksize; i++)

             s->decoded[channel][i] += (unsigned)coffset;

 
     return 0;

 }
 

 static int read_header(ShortenContext *s)
 {

     int i, ret;

     int maxnlpc = 0;
     /* shorten signature */
     if (get_bits_long(&s->gb, 32) != AV_RB32("ajkg")) {
         av_log(s->avctx, AV_LOG_ERROR, "missing shorten magic 'ajkg'\n");

         return AVERROR_INVALIDDATA;

     }
 

     s->lpcqoffset     = 0;
     s->blocksize      = DEFAULT_BLOCK_SIZE;
     s->nmean          = -1;
     s->version        = get_bits(&s->gb, 8);

     s->internal_ftype = get_uint(s, TYPESIZE);
 
     s->channels = get_uint(s, CHANSIZE);

     if (!s->channels) {
         av_log(s->avctx, AV_LOG_ERROR, "No channels reported\n");
         return AVERROR_INVALIDDATA;
     }
     if (s->channels > MAX_CHANNELS) {

         av_log(s->avctx, AV_LOG_ERROR, "too many channels: %d\n", s->channels);

         s->channels = 0;

         return AVERROR_INVALIDDATA;

     }

     s->avctx->channels = s->channels;

 
     /* get blocksize if version > 0 */
     if (s->version > 0) {

         int skip_bytes;
         unsigned blocksize;

 
         blocksize = get_uint(s, av_log2(DEFAULT_BLOCK_SIZE));
         if (!blocksize || blocksize > MAX_BLOCKSIZE) {

             av_log(s->avctx, AV_LOG_ERROR,
                    "invalid or unsupported block size: %d\n",

                    blocksize);
             return AVERROR(EINVAL);
         }
         s->blocksize = blocksize;
 

         maxnlpc  = get_uint(s, LPCQSIZE);

         if (maxnlpc > 1024U) {
             av_log(s->avctx, AV_LOG_ERROR, "maxnlpc is: %d\n", maxnlpc);
             return AVERROR_INVALIDDATA;
         }

         s->nmean = get_uint(s, 0);

         if (s->nmean > 32768U) {
             av_log(s->avctx, AV_LOG_ERROR, "nmean is: %d\n", s->nmean);
             return AVERROR_INVALIDDATA;
         }

 
         skip_bytes = get_uint(s, NSKIPSIZE);

         if ((unsigned)skip_bytes > FFMAX(get_bits_left(&s->gb), 0)/8) {

             av_log(s->avctx, AV_LOG_ERROR, "invalid skip_bytes: %d\n", skip_bytes);
             return AVERROR_INVALIDDATA;
         }
 

         for (i = 0; i < skip_bytes; i++)

             skip_bits(&s->gb, 8);
     }
     s->nwrap = FFMAX(NWRAP, maxnlpc);
 
     if (s->version > 1)
         s->lpcqoffset = V2LPCQOFFSET;
 

     if (s->avctx->extradata_size > 0)
         goto end;
 

     if (get_ur_golomb_shorten(&s->gb, FNSIZE) != FN_VERBATIM) {

         av_log(s->avctx, AV_LOG_ERROR,
                "missing verbatim section at beginning of stream\n");

         return AVERROR_INVALIDDATA;

     }
 
     s->header_size = get_ur_golomb_shorten(&s->gb, VERBATIM_CKSIZE_SIZE);

     if (s->header_size >= OUT_BUFFER_SIZE ||
         s->header_size < CANONICAL_HEADER_SIZE) {
         av_log(s->avctx, AV_LOG_ERROR, "header is wrong size: %d\n",
                s->header_size);

         return AVERROR_INVALIDDATA;

     }
 

     for (i = 0; i < s->header_size; i++)

         s->header[i] = (char)get_ur_golomb_shorten(&s->gb, VERBATIM_BYTE_SIZE);
 

     if (AV_RL32(s->header) == MKTAG('R','I','F','F')) {
         if ((ret = decode_wave_header(s->avctx, s->header, s->header_size)) < 0)
             return ret;
     } else if (AV_RL32(s->header) == MKTAG('F','O','R','M')) {
         if ((ret = decode_aiff_header(s->avctx, s->header, s->header_size)) < 0)
             return ret;
     } else {

         avpriv_report_missing_feature(s->avctx, "unsupported bit packing %"
                                       PRIX32, AV_RL32(s->header));

         return AVERROR_PATCHWELCOME;
     }

 end:

 
     if ((ret = allocate_buffers(s)) < 0)
         return ret;
 
     if ((ret = init_offset(s)) < 0)
         return ret;
 

     s->cur_chan = 0;
     s->bitshift = 0;
 

     s->got_header = 1;
 

     return 0;
 }

 static int shorten_decode_frame(AVCodecContext *avctx, void *data,
                                 int *got_frame_ptr, AVPacket *avpkt)

 {

     AVFrame *frame     = data;

     const uint8_t *buf = avpkt->data;

     int buf_size       = avpkt->size;
     ShortenContext *s  = avctx->priv_data;

     int i, input_buf_size = 0;

     int ret;
 

     /* allocate internal bitstream buffer */

     if (s->max_framesize == 0) {

         void *tmp_ptr;

         s->max_framesize = 8192; // should hopefully be enough for the first header

         tmp_ptr = av_fast_realloc(s->bitstream, &s->allocated_bitstream_size,

                                   s->max_framesize + AV_INPUT_BUFFER_PADDING_SIZE);

         if (!tmp_ptr) {

             s->max_framesize = 0;

             av_log(avctx, AV_LOG_ERROR, "error allocating bitstream buffer\n");
             return AVERROR(ENOMEM);
         }

         memset(tmp_ptr, 0, s->allocated_bitstream_size);

         s->bitstream = tmp_ptr;

     }
 

     /* append current packet data to bitstream buffer */

     buf_size       = FFMIN(buf_size, s->max_framesize - s->bitstream_size);
     input_buf_size = buf_size;
 
     if (s->bitstream_index + s->bitstream_size + buf_size + AV_INPUT_BUFFER_PADDING_SIZE >
         s->allocated_bitstream_size) {
         memmove(s->bitstream, &s->bitstream[s->bitstream_index],
                 s->bitstream_size);
         s->bitstream_index = 0;
     }
     if (buf)
         memcpy(&s->bitstream[s->bitstream_index + s->bitstream_size], buf,
                buf_size);
     buf               = &s->bitstream[s->bitstream_index];
     buf_size         += s->bitstream_size;
     s->bitstream_size = buf_size;
 
     /* do not decode until buffer has at least max_framesize bytes or
      * the end of the file has been reached */
     if (buf_size < s->max_framesize && avpkt->data) {
         *got_frame_ptr = 0;
         return input_buf_size;

     }

     /* init and position bitstream reader */

     if ((ret = init_get_bits8(&s->gb, buf, buf_size)) < 0)
         return ret;

     skip_bits(&s->gb, s->bitindex);

     /* process header or next subblock */

     if (!s->got_header) {

         if ((ret = read_header(s)) < 0)
             return ret;

         if (avpkt->size) {

             int max_framesize;
             void *tmp_ptr;
 

             max_framesize = FFMAX(s->max_framesize, s->blocksize * s->channels * 8);

             tmp_ptr = av_fast_realloc(s->bitstream, &s->allocated_bitstream_size,
                                       max_framesize + AV_INPUT_BUFFER_PADDING_SIZE);
             if (!tmp_ptr) {
                 av_log(avctx, AV_LOG_ERROR, "error allocating bitstream buffer\n");
                 return AVERROR(ENOMEM);
             }
             s->bitstream = tmp_ptr;
             s->max_framesize = max_framesize;

             *got_frame_ptr = 0;
             goto finish_frame;
         }

     }
 

     /* if quit command was read previously, don't decode anything */
     if (s->got_quit_command) {

         *got_frame_ptr = 0;

         return avpkt->size;
     }

     s->cur_chan = 0;
     while (s->cur_chan < s->channels) {

         unsigned cmd;

         int len;
 

         if (get_bits_left(&s->gb) < 3 + FNSIZE) {

             *got_frame_ptr = 0;

             break;

         }
 
         cmd = get_ur_golomb_shorten(&s->gb, FNSIZE);
 

         if (cmd > FN_VERBATIM) {
             av_log(avctx, AV_LOG_ERROR, "unknown shorten function %d\n", cmd);

             *got_frame_ptr = 0;

             break;

         }
 

         if (!is_audio_command[cmd]) {
             /* process non-audio command */
             switch (cmd) {

             case FN_VERBATIM:
                 len = get_ur_golomb_shorten(&s->gb, VERBATIM_CKSIZE_SIZE);

                 if (len < 0 || len > get_bits_left(&s->gb)) {
                     av_log(avctx, AV_LOG_ERROR, "verbatim length %d invalid\n",
                            len);
                     return AVERROR_INVALIDDATA;
                 }

                 while (len--)
                     get_ur_golomb_shorten(&s->gb, VERBATIM_BYTE_SIZE);
                 break;

             case FN_BITSHIFT: {
                 unsigned bitshift = get_ur_golomb_shorten(&s->gb, BITSHIFTSIZE);

                 if (bitshift > 32) {

                     av_log(avctx, AV_LOG_ERROR, "bitshift %d is invalid\n",
                            bitshift);

                     return AVERROR_INVALIDDATA;

                 }
                 s->bitshift = bitshift;

                 break;

             }

             case FN_BLOCKSIZE: {

                 unsigned blocksize = get_uint(s, av_log2(s->blocksize));

                 if (blocksize > s->blocksize) {

                     avpriv_report_missing_feature(avctx,
                                                   "Increasing block size");

                     return AVERROR_PATCHWELCOME;

                 }

                 if (!blocksize || blocksize > MAX_BLOCKSIZE) {
                     av_log(avctx, AV_LOG_ERROR, "invalid or unsupported "
                                                 "block size: %d\n", blocksize);
                     return AVERROR(EINVAL);
                 }
                 s->blocksize = blocksize;
                 break;
             }
             case FN_QUIT:
                 s->got_quit_command = 1;
                 break;

             }

             if (cmd == FN_QUIT)

                 break;

         } else {
             /* process audio command */

             int residual_size = 0;
             int channel = s->cur_chan;
             int32_t coffset;

 
             /* get Rice code for residual decoding */

             if (cmd != FN_ZERO) {
                 residual_size = get_ur_golomb_shorten(&s->gb, ENERGYSIZE);

                 /* This is a hack as version 0 differed in the definition
                  * of get_sr_golomb_shorten(). */

                 if (s->version == 0)
                     residual_size--;

                 if (residual_size > 30U) {
                     av_log(avctx, AV_LOG_ERROR, "residual size unsupportd: %d\n", residual_size);
                     return AVERROR_INVALIDDATA;
                 }

             }

             /* calculate sample offset using means from previous blocks */

             if (s->nmean == 0)
                 coffset = s->offset[channel][0];
             else {
                 int32_t sum = (s->version < 2) ? 0 : s->nmean / 2;

                 for (i = 0; i < s->nmean; i++)

                     sum += (unsigned)s->offset[channel][i];

                 coffset = sum / s->nmean;
                 if (s->version >= 2)

                     coffset = s->bitshift == 0 ? coffset : coffset >> s->bitshift - 1 >> 1;

             }

             /* decode samples for this channel */

             if (cmd == FN_ZERO) {

                 for (i = 0; i < s->blocksize; i++)

                     s->decoded[channel][i] = 0;
             } else {

                 if ((ret = decode_subframe_lpc(s, cmd, channel,
                                                residual_size, coffset)) < 0)

                     return ret;

             }

             /* update means with info from the current block */

             if (s->nmean > 0) {

                 int64_t sum = (s->version < 2) ? 0 : s->blocksize / 2;

                 for (i = 0; i < s->blocksize; i++)

                     sum += s->decoded[channel][i];

                 for (i = 1; i < s->nmean; i++)
                     s->offset[channel][i - 1] = s->offset[channel][i];

                 if (s->version < 2)
                     s->offset[channel][s->nmean - 1] = sum / s->blocksize;
                 else

                     s->offset[channel][s->nmean - 1] = s->bitshift == 32 ? 0 : (sum / s->blocksize) * (1LL << s->bitshift);

             }

             /* copy wrap samples for use with next block */

             for (i = -s->nwrap; i < 0; i++)

                 s->decoded[channel][i] = s->decoded[channel][i + s->blocksize];

             /* shift samples to add in unused zero bits which were removed

              * during encoding */

             fix_bitshift(s, s->decoded[channel]);

             /* if this is the last channel in the block, output the samples */

             s->cur_chan++;
             if (s->cur_chan == s->channels) {

                 uint8_t *samples_u8;
                 int16_t *samples_s16;
                 int chan;
 

                 /* get output buffer */

                 frame->nb_samples = s->blocksize;

                 if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)

                     return ret;

 
                 for (chan = 0; chan < s->channels; chan++) {

                     samples_u8  = ((uint8_t **)frame->extended_data)[chan];
                     samples_s16 = ((int16_t **)frame->extended_data)[chan];

                     for (i = 0; i < s->blocksize; i++) {

                         switch (s->internal_ftype) {
                         case TYPE_U8:
                             *samples_u8++ = av_clip_uint8(s->decoded[chan][i]);
                             break;
                         case TYPE_S16HL:
                         case TYPE_S16LH:
                             *samples_s16++ = av_clip_int16(s->decoded[chan][i]);
                             break;
                         }
                     }

                     if (s->swap && s->internal_ftype != TYPE_U8)
                         s->bdsp.bswap16_buf(((uint16_t **)frame->extended_data)[chan],
                                             ((uint16_t **)frame->extended_data)[chan],
                                             s->blocksize);
 

                 }

                 *got_frame_ptr = 1;

             }

         }
     }

     if (s->cur_chan < s->channels)

         *got_frame_ptr = 0;

 finish_frame:

     s->bitindex = get_bits_count(&s->gb) - 8 * (get_bits_count(&s->gb) / 8);
     i           = get_bits_count(&s->gb) / 8;

     if (i > buf_size) {
         av_log(s->avctx, AV_LOG_ERROR, "overread: %d\n", i - buf_size);

         s->bitstream_size  = 0;
         s->bitstream_index = 0;

         return AVERROR_INVALIDDATA;

     }
     if (s->bitstream_size) {
         s->bitstream_index += i;
         s->bitstream_size  -= i;
         return input_buf_size;
     } else
         return i;
 }
 

 static av_cold int shorten_decode_close(AVCodecContext *avctx)

 {
     ShortenContext *s = avctx->priv_data;
     int i;
 
     for (i = 0; i < s->channels; i++) {

         s->decoded[i] = NULL;
         av_freep(&s->decoded_base[i]);

         av_freep(&s->offset[i]);
     }
     av_freep(&s->bitstream);

     av_freep(&s->coeffs);

     return 0;
 }
 

 AVCodec ff_shorten_decoder = {

     .name           = "shorten",

     .long_name      = NULL_IF_CONFIG_SMALL("Shorten"),

     .type           = AVMEDIA_TYPE_AUDIO,

     .id             = AV_CODEC_ID_SHORTEN,

     .priv_data_size = sizeof(ShortenContext),
     .init           = shorten_decode_init,
     .close          = shorten_decode_close,
     .decode         = shorten_decode_frame,

     .capabilities   = AV_CODEC_CAP_SUBFRAMES | AV_CODEC_CAP_DELAY | AV_CODEC_CAP_DR1,

     .sample_fmts    = (const enum AVSampleFormat[]) { AV_SAMPLE_FMT_S16P,

                                                       AV_SAMPLE_FMT_U8P,

                                                       AV_SAMPLE_FMT_NONE },

 };