/*

  * H.264 MP4 to Annex B byte stream format filter

  * Copyright (c) 2007 Benoit Fouet <benoit.fouet@free.fr>

  *
  * 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
  */
 

 #include "libavutil/intreadwrite.h"

 #include "avcodec.h"
 
 typedef struct H264BSFContext {
     uint8_t  length_size;
     uint8_t  first_idr;

     int      extradata_parsed;

 } H264BSFContext;
 

 static int alloc_and_copy(uint8_t **poutbuf,          int *poutbuf_size,

                           const uint8_t *sps_pps, uint32_t sps_pps_size,
                           const uint8_t *in,      uint32_t in_size) {

     uint32_t offset = *poutbuf_size;
     uint8_t nal_header_size = offset ? 3 : 4;

     void *tmp;

 
     *poutbuf_size += sps_pps_size+in_size+nal_header_size;

     tmp = av_realloc(*poutbuf, *poutbuf_size);
     if (!tmp)
         return AVERROR(ENOMEM);
     *poutbuf = tmp;

     if (sps_pps)
         memcpy(*poutbuf+offset, sps_pps, sps_pps_size);
     memcpy(*poutbuf+sps_pps_size+nal_header_size+offset, in, in_size);

     if (!offset) {

         AV_WB32(*poutbuf+sps_pps_size, 1);

     } else {

         (*poutbuf+offset+sps_pps_size)[0] = (*poutbuf+offset+sps_pps_size)[1] = 0;
         (*poutbuf+offset+sps_pps_size)[2] = 1;

     }

 
     return 0;

 }
 
 static int h264_mp4toannexb_filter(AVBitStreamFilterContext *bsfc,
                                    AVCodecContext *avctx, const char *args,
                                    uint8_t  **poutbuf, int *poutbuf_size,
                                    const uint8_t *buf, int      buf_size,
                                    int keyframe) {
     H264BSFContext *ctx = bsfc->priv_data;

     int i;

     uint8_t unit_type;

     int32_t nal_size;
     uint32_t cumul_size = 0;
     const uint8_t *buf_end = buf + buf_size;

     int ret = AVERROR(EINVAL);

 
     /* nothing to filter */
     if (!avctx->extradata || avctx->extradata_size < 6) {
         *poutbuf = (uint8_t*) buf;
         *poutbuf_size = buf_size;
         return 0;
     }
 
     /* retrieve sps and pps NAL units from extradata */

     if (!ctx->extradata_parsed) {

         uint16_t unit_size;

         uint64_t total_size = 0;

         uint8_t *out = NULL, unit_nb, sps_done = 0, sps_seen = 0, pps_seen = 0;

         const uint8_t *extradata = avctx->extradata+4;
         static const uint8_t nalu_header[4] = {0, 0, 0, 1};
 
         /* retrieve length coded size */
         ctx->length_size = (*extradata++ & 0x3) + 1;
 
         /* retrieve sps and pps unit(s) */
         unit_nb = *extradata++ & 0x1f; /* number of sps unit(s) */
         if (!unit_nb) {

             goto pps;

         } else {

             sps_seen = 1;

         }

         while (unit_nb--) {

             void *tmp;
 

             unit_size = AV_RB16(extradata);
             total_size += unit_size+4;

             if (total_size > INT_MAX - FF_INPUT_BUFFER_PADDING_SIZE ||
                 extradata+2+unit_size > avctx->extradata+avctx->extradata_size) {

                 av_free(out);
                 return AVERROR(EINVAL);
             }

             tmp = av_realloc(out, total_size + FF_INPUT_BUFFER_PADDING_SIZE);
             if (!tmp) {
                 av_free(out);

                 return AVERROR(ENOMEM);

             }
             out = tmp;

             memcpy(out+total_size-unit_size-4, nalu_header, 4);
             memcpy(out+total_size-unit_size,   extradata+2, unit_size);
             extradata += 2+unit_size;

 pps:

             if (!unit_nb && !sps_done++) {

                 unit_nb = *extradata++; /* number of pps unit(s) */

                 if (unit_nb)
                     pps_seen = 1;
             }

         }
 

         if(out)
             memset(out + total_size, 0, FF_INPUT_BUFFER_PADDING_SIZE);
 
         if (!sps_seen)
             av_log(avctx, AV_LOG_WARNING, "Warning: SPS NALU missing or invalid. The resulting stream may not play.\n");
         if (!pps_seen)
             av_log(avctx, AV_LOG_WARNING, "Warning: PPS NALU missing or invalid. The resulting stream may not play.\n");
 

         av_free(avctx->extradata);
         avctx->extradata      = out;
         avctx->extradata_size = total_size;
         ctx->first_idr        = 1;
         ctx->extradata_parsed = 1;

     }
 
     *poutbuf_size = 0;
     *poutbuf = NULL;
     do {

         ret= AVERROR(EINVAL);

         if (buf + ctx->length_size > buf_end)
             goto fail;
 

         for (nal_size = 0, i = 0; i<ctx->length_size; i++)
             nal_size = (nal_size << 8) | buf[i];

 
         buf += ctx->length_size;
         unit_type = *buf & 0x1f;
 

         if (buf + nal_size > buf_end || nal_size < 0)
             goto fail;
 

         /* prepend only to the first type 5 NAL unit of an IDR picture */
         if (ctx->first_idr && unit_type == 5) {

             if ((ret=alloc_and_copy(poutbuf, poutbuf_size,

                                avctx->extradata, avctx->extradata_size,

                                buf, nal_size)) < 0)

                 goto fail;

             ctx->first_idr = 0;

         } else {

             if ((ret=alloc_and_copy(poutbuf, poutbuf_size,

                                NULL, 0,

                                buf, nal_size)) < 0)

                 goto fail;

             if (!ctx->first_idr && unit_type == 1)
                 ctx->first_idr = 1;
         }
 
         buf += nal_size;
         cumul_size += nal_size + ctx->length_size;
     } while (cumul_size < buf_size);
 
     return 1;

 
 fail:
     av_freep(poutbuf);
     *poutbuf_size = 0;

     return ret;

 }
 

 AVBitStreamFilter ff_h264_mp4toannexb_bsf = {

     "h264_mp4toannexb",
     sizeof(H264BSFContext),
     h264_mp4toannexb_filter,
 };