text: /*
   * 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 <string.h>
  
  #include "libavutil/intreadwrite.h"
  #include "libavutil/mem.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 + FF_INPUT_BUFFER_PADDING_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_extradata_to_annexb(AVCodecContext *avctx, const int padding)
  {
      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 };
      int length_size = (*extradata++ & 0x3) + 1; // retrieve length coded size
  
      /* 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 - padding ||
              extradata + 2 + unit_size > avctx->extradata +
              avctx->extradata_size) {
              av_free(out);
              return AVERROR(EINVAL);
          }
          tmp = av_realloc(out, total_size + padding);
          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;
  
      return length_size;
  }
  
  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 = 0;
  
      /* 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) {
          ret = h264_extradata_to_annexb(avctx, FF_INPUT_BUFFER_PADDING_SIZE);
          if (ret < 0)
              return ret;
          ctx->length_size      = ret;
          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,
  };
  