/*

  * 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"

 #include "bsf.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;

 } H264BSFContext;
 

 static int alloc_and_copy(AVPacket *out,

                           const uint8_t *sps_pps, uint32_t sps_pps_size,

                           const uint8_t *in, uint32_t in_size)
 {

     uint32_t offset         = out->size;

     uint8_t nal_header_size = offset ? 3 : 4;

     int err;

     err = av_grow_packet(out, sps_pps_size + in_size + nal_header_size);
     if (err < 0)

         return err;

     if (sps_pps)

         memcpy(out->data + offset, sps_pps, sps_pps_size);
     memcpy(out->data + sps_pps_size + nal_header_size + offset, in, in_size);

     if (!offset) {

         AV_WB32(out->data + sps_pps_size, 1);

     } else {

         (out->data + offset + sps_pps_size)[0] =
         (out->data + offset + sps_pps_size)[1] = 0;
         (out->data + offset + sps_pps_size)[2] = 1;

     }

 
     return 0;

 }
 

 static int h264_extradata_to_annexb(AVBSFContext *ctx, const int padding)

 {

     H264BSFContext *s = ctx->priv_data;

     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            = ctx->par_in->extradata + 4;

     static const uint8_t nalu_header[4] = { 0, 0, 0, 1 };
     int length_size = (*extradata++ & 0x3) + 1; // retrieve length coded size
 

     s->sps_offset = s->pps_offset = -1;

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

         goto pps;

     } else {

         s->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(ctx, 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 > ctx->par_in->extradata + ctx->par_in->extradata_size) {
             av_log(ctx, 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) {

                 s->pps_offset = total_size;

                 pps_seen = 1;

             }

         }
     }
 
     if (out)

         memset(out + total_size, 0, padding);

 
     if (!sps_seen)

         av_log(ctx, AV_LOG_WARNING,

                "Warning: SPS NALU missing or invalid. "
                "The resulting stream may not play.\n");
 
     if (!pps_seen)

         av_log(ctx, AV_LOG_WARNING,

                "Warning: PPS NALU missing or invalid. "
                "The resulting stream may not play.\n");
 

     av_freep(&ctx->par_out->extradata);
     ctx->par_out->extradata      = out;
     ctx->par_out->extradata_size = total_size;

 
     return length_size;
 }
 

 static int h264_mp4toannexb_init(AVBSFContext *ctx)

 {

     H264BSFContext *s = ctx->priv_data;

     int extra_size = ctx->par_in->extradata_size;

     int ret;
 
     /* retrieve sps and pps NAL units from extradata */

     if (!extra_size                                               ||
         (extra_size >= 3 && AV_RB24(ctx->par_in->extradata) == 1) ||
         (extra_size >= 4 && AV_RB32(ctx->par_in->extradata) == 1)) {
         av_log(ctx, AV_LOG_VERBOSE,
                "The input looks like it is Annex B already\n");
     } else if (extra_size >= 6) {

         ret = h264_extradata_to_annexb(ctx, AV_INPUT_BUFFER_PADDING_SIZE);
         if (ret < 0)
             return ret;
 
         s->length_size      = ret;

         s->new_idr          = 1;
         s->idr_sps_seen     = 0;
         s->idr_pps_seen     = 0;

         s->extradata_parsed = 1;

     } else {
         av_log(ctx, AV_LOG_ERROR, "Invalid extradata size: %d\n", extra_size);
         return AVERROR_INVALIDDATA;

     }
 
     return 0;
 }
 
 static int h264_mp4toannexb_filter(AVBSFContext *ctx, AVPacket *out)
 {
     H264BSFContext *s = ctx->priv_data;
 
     AVPacket *in;

     uint8_t unit_type;

     int32_t nal_size;

     uint32_t cumul_size    = 0;

     const uint8_t *buf;
     const uint8_t *buf_end;
     int            buf_size;

     int ret = 0, i;

     ret = ff_bsf_get_packet(ctx, &in);
     if (ret < 0)
         return ret;

 
     /* nothing to filter */

     if (!s->extradata_parsed) {
         av_packet_move_ref(out, in);
         av_packet_free(&in);

         return 0;
     }
 

     buf      = in->data;
     buf_size = in->size;
     buf_end  = in->data + in->size;

     do {

         ret= AVERROR(EINVAL);

         if (buf + s->length_size > buf_end)

             goto fail;
 

         for (nal_size = 0, i = 0; i<s->length_size; i++)

             nal_size = (nal_size << 8) | buf[i];

         buf += s->length_size;

         unit_type = *buf & 0x1f;
 

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

             goto fail;
 

         if (unit_type == 7)

             s->idr_sps_seen = s->new_idr = 1;

         else if (unit_type == 8) {

             s->idr_pps_seen = s->new_idr = 1;

             /* if SPS has not been seen yet, prepend the AVCC one to PPS */

             if (!s->idr_sps_seen) {
                 if (s->sps_offset == -1)
                     av_log(ctx, AV_LOG_WARNING, "SPS not present in the stream, nor in AVCC, stream may be unreadable\n");

                 else {

                     if ((ret = alloc_and_copy(out,
                                          ctx->par_out->extradata + s->sps_offset,
                                          s->pps_offset != -1 ? s->pps_offset : ctx->par_out->extradata_size - s->sps_offset,

                                          buf, nal_size)) < 0)
                         goto fail;

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

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

         if (s->new_idr && unit_type == 5 && !s->idr_sps_seen && !s->idr_pps_seen) {
             if ((ret=alloc_and_copy(out,

                                ctx->par_out->extradata, ctx->par_out->extradata_size,

                                buf, nal_size)) < 0)

                 goto fail;

             s->new_idr = 0;

         /* if only SPS has been seen, also insert PPS */

         } else if (s->new_idr && unit_type == 5 && s->idr_sps_seen && !s->idr_pps_seen) {
             if (s->pps_offset == -1) {
                 av_log(ctx, AV_LOG_WARNING, "PPS not present in the stream, nor in AVCC, stream may be unreadable\n");
                 if ((ret = alloc_and_copy(out, NULL, 0, buf, nal_size)) < 0)

                     goto fail;

             } else if ((ret = alloc_and_copy(out,
                                         ctx->par_out->extradata + s->pps_offset, ctx->par_out->extradata_size - s->pps_offset,

                                         buf, nal_size)) < 0)
                 goto fail;

         } else {

             if ((ret=alloc_and_copy(out, NULL, 0, buf, nal_size)) < 0)

                 goto fail;

             if (!s->new_idr && unit_type == 1) {
                 s->new_idr = 1;
                 s->idr_sps_seen = 0;
                 s->idr_pps_seen = 0;

             }

         }
 

 next_nal:

         buf        += nal_size;

         cumul_size += nal_size + s->length_size;

     } while (cumul_size < buf_size);
 

     ret = av_packet_copy_props(out, in);
     if (ret < 0)
         goto fail;

 
 fail:

     if (ret < 0)
         av_packet_unref(out);
     av_packet_free(&in);
 

     return ret;

 }
 

 static const enum AVCodecID codec_ids[] = {
     AV_CODEC_ID_H264, AV_CODEC_ID_NONE,
 };

 const AVBitStreamFilter ff_h264_mp4toannexb_bsf = {

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

     .init           = h264_mp4toannexb_init,

     .filter         = h264_mp4toannexb_filter,

     .codec_ids      = codec_ids,

 };