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libavcodec/h264_mp4toannexb_bsf.c

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00001 /*
00002  * H.264 MP4 to Annex B byte stream format filter
00003  * Copyright (c) 2007 Benoit Fouet <benoit.fouet@free.fr>
00004  *
00005  * This file is part of FFmpeg.
00006  *
00007  * FFmpeg is free software; you can redistribute it and/or
00008  * modify it under the terms of the GNU Lesser General Public
00009  * License as published by the Free Software Foundation; either
00010  * version 2.1 of the License, or (at your option) any later version.
00011  *
00012  * FFmpeg is distributed in the hope that it will be useful,
00013  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00014  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00015  * Lesser General Public License for more details.
00016  *
00017  * You should have received a copy of the GNU Lesser General Public
00018  * License along with FFmpeg; if not, write to the Free Software
00019  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00020  */
00021 
00022 #include "libavutil/intreadwrite.h"
00023 #include "avcodec.h"
00024 
00025 typedef struct H264BSFContext {
00026     uint8_t  length_size;
00027     uint8_t  first_idr;
00028     uint8_t *sps_pps_data;
00029     uint32_t size;
00030 } H264BSFContext;
00031 
00032 static void alloc_and_copy(uint8_t **poutbuf,          int *poutbuf_size,
00033                            const uint8_t *sps_pps, uint32_t sps_pps_size,
00034                            const uint8_t *in,      uint32_t in_size) {
00035     uint32_t offset = *poutbuf_size;
00036     uint8_t nal_header_size = offset ? 3 : 4;
00037 
00038     *poutbuf_size += sps_pps_size+in_size+nal_header_size;
00039     *poutbuf = av_realloc(*poutbuf, *poutbuf_size);
00040     if (sps_pps)
00041         memcpy(*poutbuf+offset, sps_pps, sps_pps_size);
00042     memcpy(*poutbuf+sps_pps_size+nal_header_size+offset, in, in_size);
00043     if (!offset)
00044         AV_WB32(*poutbuf+sps_pps_size, 1);
00045     else {
00046         (*poutbuf+offset+sps_pps_size)[0] = (*poutbuf+offset+sps_pps_size)[1] = 0;
00047         (*poutbuf+offset+sps_pps_size)[2] = 1;
00048     }
00049 }
00050 
00051 static int h264_mp4toannexb_filter(AVBitStreamFilterContext *bsfc,
00052                                    AVCodecContext *avctx, const char *args,
00053                                    uint8_t  **poutbuf, int *poutbuf_size,
00054                                    const uint8_t *buf, int      buf_size,
00055                                    int keyframe) {
00056     H264BSFContext *ctx = bsfc->priv_data;
00057     uint8_t unit_type;
00058     int32_t nal_size;
00059     uint32_t cumul_size = 0;
00060     const uint8_t *buf_end = buf + buf_size;
00061 
00062     /* nothing to filter */
00063     if (!avctx->extradata || avctx->extradata_size < 6) {
00064         *poutbuf = (uint8_t*) buf;
00065         *poutbuf_size = buf_size;
00066         return 0;
00067     }
00068 
00069     /* retrieve sps and pps NAL units from extradata */
00070     if (!ctx->sps_pps_data) {
00071         uint16_t unit_size;
00072         uint32_t total_size = 0;
00073         uint8_t *out = NULL, unit_nb, sps_done = 0;
00074         const uint8_t *extradata = avctx->extradata+4;
00075         static const uint8_t nalu_header[4] = {0, 0, 0, 1};
00076 
00077         /* retrieve length coded size */
00078         ctx->length_size = (*extradata++ & 0x3) + 1;
00079         if (ctx->length_size == 3)
00080             return AVERROR(EINVAL);
00081 
00082         /* retrieve sps and pps unit(s) */
00083         unit_nb = *extradata++ & 0x1f; /* number of sps unit(s) */
00084         if (!unit_nb) {
00085             unit_nb = *extradata++; /* number of pps unit(s) */
00086             sps_done++;
00087         }
00088         while (unit_nb--) {
00089             unit_size = AV_RB16(extradata);
00090             total_size += unit_size+4;
00091             if (extradata+2+unit_size > avctx->extradata+avctx->extradata_size) {
00092                 av_free(out);
00093                 return AVERROR(EINVAL);
00094             }
00095             out = av_realloc(out, total_size);
00096             if (!out)
00097                 return AVERROR(ENOMEM);
00098             memcpy(out+total_size-unit_size-4, nalu_header, 4);
00099             memcpy(out+total_size-unit_size,   extradata+2, unit_size);
00100             extradata += 2+unit_size;
00101 
00102             if (!unit_nb && !sps_done++)
00103                 unit_nb = *extradata++; /* number of pps unit(s) */
00104         }
00105 
00106         ctx->sps_pps_data = out;
00107         ctx->size = total_size;
00108         ctx->first_idr = 1;
00109     }
00110 
00111     *poutbuf_size = 0;
00112     *poutbuf = NULL;
00113     do {
00114         if (buf + ctx->length_size > buf_end)
00115             goto fail;
00116 
00117         if (ctx->length_size == 1)
00118             nal_size = buf[0];
00119         else if (ctx->length_size == 2)
00120             nal_size = AV_RB16(buf);
00121         else
00122             nal_size = AV_RB32(buf);
00123 
00124         buf += ctx->length_size;
00125         unit_type = *buf & 0x1f;
00126 
00127         if (buf + nal_size > buf_end || nal_size < 0)
00128             goto fail;
00129 
00130         /* prepend only to the first type 5 NAL unit of an IDR picture */
00131         if (ctx->first_idr && unit_type == 5) {
00132             alloc_and_copy(poutbuf, poutbuf_size,
00133                            ctx->sps_pps_data, ctx->size,
00134                            buf, nal_size);
00135             ctx->first_idr = 0;
00136         }
00137         else {
00138             alloc_and_copy(poutbuf, poutbuf_size,
00139                            NULL, 0,
00140                            buf, nal_size);
00141             if (!ctx->first_idr && unit_type == 1)
00142                 ctx->first_idr = 1;
00143         }
00144 
00145         buf += nal_size;
00146         cumul_size += nal_size + ctx->length_size;
00147     } while (cumul_size < buf_size);
00148 
00149     return 1;
00150 
00151 fail:
00152     av_freep(poutbuf);
00153     *poutbuf_size = 0;
00154     return AVERROR(EINVAL);
00155 }
00156 
00157 static void h264_mp4toannexb_close(AVBitStreamFilterContext *bsfc)
00158 {
00159     H264BSFContext *ctx = bsfc->priv_data;
00160     av_freep(&ctx->sps_pps_data);
00161 }
00162 
00163 AVBitStreamFilter h264_mp4toannexb_bsf = {
00164     "h264_mp4toannexb",
00165     sizeof(H264BSFContext),
00166     h264_mp4toannexb_filter,
00167     h264_mp4toannexb_close,
00168 };
00169 

Generated on Fri Sep 16 2011 17:17:37 for FFmpeg by  doxygen 1.7.1