/*

  * 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 {

     int32_t  sps_offset;
     int32_t  pps_offset;

     uint8_t  length_size;

     uint8_t  new_idr;

     uint8_t  idr_sps_seen;
     uint8_t  idr_pps_seen;

     int      extradata_parsed;

 
     /* When private_spspps is zero then spspps_buf points to global extradata
        and bsf does replace a global extradata to own-allocated version (default
        behaviour).
        When private_spspps is non-zero the bsf uses a private version of spspps buf.
        This mode necessary when bsf uses in decoder, else bsf has issues after
        decoder re-initialization. Use the "private_spspps_buf" argument to
        activate this mode.
      */
     int      private_spspps;
     uint8_t *spspps_buf;
     uint32_t spspps_size;

 } 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;

     int err;

     *poutbuf_size += sps_pps_size + in_size + nal_header_size;

     if ((err = av_reallocp(poutbuf,

                            *poutbuf_size + AV_INPUT_BUFFER_PADDING_SIZE)) < 0) {

         *poutbuf_size = 0;
         return err;
     }

     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(H264BSFContext *ctx, 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
 

     ctx->sps_offset = ctx->pps_offset = -1;
 

     /* retrieve sps and pps unit(s) */
     unit_nb = *extradata++ & 0x1f; /* number of sps unit(s) */
     if (!unit_nb) {

         goto pps;

     } else {

         ctx->sps_offset = 0;

         sps_seen = 1;
     }
 
     while (unit_nb--) {

         int err;

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

         if (total_size > INT_MAX - padding) {
             av_log(avctx, AV_LOG_ERROR,
                    "Too big extradata size, corrupted stream or invalid MP4/AVCC bitstream\n");
             av_free(out);
             return AVERROR(EINVAL);
         }
         if (extradata + 2 + unit_size > avctx->extradata + avctx->extradata_size) {
             av_log(avctx, AV_LOG_ERROR, "Packet header is not contained in global extradata, "
                    "corrupted stream or invalid MP4/AVCC bitstream\n");

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

         if ((err = av_reallocp(&out, total_size + padding)) < 0)
             return err;

         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) {

                 ctx->pps_offset = total_size;

                 pps_seen = 1;

             }

         }
     }
 
     if (out)

         memset(out + total_size, 0, padding);

 
     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");
 

     if (!ctx->private_spspps) {
         av_free(avctx->extradata);
         avctx->extradata      = out;
         avctx->extradata_size = total_size;
     }
     ctx->spspps_buf  = out;
     ctx->spspps_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) {

         if (args && strstr(args, "private_spspps_buf"))
             ctx->private_spspps = 1;
 

         ret = h264_extradata_to_annexb(ctx, avctx, AV_INPUT_BUFFER_PADDING_SIZE);

         if (ret < 0)
             return ret;
         ctx->length_size      = ret;

         ctx->new_idr          = 1;

         ctx->idr_sps_seen     = 0;
         ctx->idr_pps_seen     = 0;

         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 (nal_size > buf_end - buf || nal_size < 0)

             goto fail;
 

         if (unit_type == 7)

             ctx->idr_sps_seen = ctx->new_idr = 1;

         else if (unit_type == 8) {

             ctx->idr_pps_seen = ctx->new_idr = 1;

             /* if SPS has not been seen yet, prepend the AVCC one to PPS */
             if (!ctx->idr_sps_seen) {
                 if (ctx->sps_offset == -1)
                     av_log(avctx, AV_LOG_WARNING, "SPS not present in the stream, nor in AVCC, stream may be unreadable\n");
                 else {
                     if ((ret = alloc_and_copy(poutbuf, poutbuf_size,

                                          ctx->spspps_buf + ctx->sps_offset,
                                          ctx->pps_offset != -1 ? ctx->pps_offset : ctx->spspps_size - ctx->sps_offset,

                                          buf, nal_size)) < 0)
                         goto fail;
                     ctx->idr_sps_seen = 1;
                     goto next_nal;
                 }
             }
         }

         /* if this is a new IDR picture following an IDR picture, reset the idr flag.
          * Just check first_mb_in_slice to be 0 as this is the simplest solution.
          * This could be checking idr_pic_id instead, but would complexify the parsing. */

         if (!ctx->new_idr && unit_type == 5 && (buf[1] & 0x80))
             ctx->new_idr = 1;

 
         /* prepend only to the first type 5 NAL unit of an IDR picture, if no sps/pps are already present */

         if (ctx->new_idr && unit_type == 5 && !ctx->idr_sps_seen && !ctx->idr_pps_seen) {

             if ((ret=alloc_and_copy(poutbuf, poutbuf_size,

                                ctx->spspps_buf, ctx->spspps_size,

                                buf, nal_size)) < 0)

                 goto fail;

             ctx->new_idr = 0;

         /* if only SPS has been seen, also insert PPS */
         } else if (ctx->new_idr && unit_type == 5 && ctx->idr_sps_seen && !ctx->idr_pps_seen) {
             if (ctx->pps_offset == -1) {
                 av_log(avctx, AV_LOG_WARNING, "PPS not present in the stream, nor in AVCC, stream may be unreadable\n");
                 if ((ret = alloc_and_copy(poutbuf, poutbuf_size,
                                      NULL, 0, buf, nal_size)) < 0)
                     goto fail;
             } else if ((ret = alloc_and_copy(poutbuf, poutbuf_size,

                                         ctx->spspps_buf + ctx->pps_offset, ctx->spspps_size - ctx->pps_offset,

                                         buf, nal_size)) < 0)
                 goto fail;

         } else {

             if ((ret=alloc_and_copy(poutbuf, poutbuf_size,

                                NULL, 0, buf, nal_size)) < 0)

                 goto fail;

             if (!ctx->new_idr && unit_type == 1) {
                 ctx->new_idr = 1;

                 ctx->idr_sps_seen = 0;
                 ctx->idr_pps_seen = 0;

             }

         }
 

 next_nal:

         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;

 }
 

 static void h264_mp4toannexb_filter_close(AVBitStreamFilterContext *bsfc)
 {
     H264BSFContext *ctx = bsfc->priv_data;
     if (ctx->private_spspps)

         av_freep(&ctx->spspps_buf);

 }
 

 AVBitStreamFilter ff_h264_mp4toannexb_bsf = {

     .name           = "h264_mp4toannexb",
     .priv_data_size = sizeof(H264BSFContext),
     .filter         = h264_mp4toannexb_filter,

     .close          = h264_mp4toannexb_filter_close,

 };