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ffmpeg / libavcodec / h264_mp4toannexb_bsf.c @ d5cc1ed7

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/*
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 * H.264 MP4 to Annex B byte stream format filter
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 * Copyright (c) 2007 Benoit Fouet <benoit.fouet@free.fr>
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 *
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 * This file is part of FFmpeg.
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 *
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 * FFmpeg is free software; you can redistribute it and/or
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 * modify it under the terms of the GNU Lesser General Public
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 * License as published by the Free Software Foundation; either
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 * version 2.1 of the License, or (at your option) any later version.
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 *
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 * FFmpeg is distributed in the hope that it will be useful,
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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 * Lesser General Public License for more details.
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 *
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 * You should have received a copy of the GNU Lesser General Public
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 * License along with FFmpeg; if not, write to the Free Software
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 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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 */
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#include "libavutil/intreadwrite.h"
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#include "avcodec.h"
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typedef struct H264BSFContext {
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    uint8_t  length_size;
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    uint8_t  first_idr;
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    int      extradata_parsed;
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} H264BSFContext;
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static void alloc_and_copy(uint8_t **poutbuf,          int *poutbuf_size,
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                           const uint8_t *sps_pps, uint32_t sps_pps_size,
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                           const uint8_t *in,      uint32_t in_size) {
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    uint32_t offset = *poutbuf_size;
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    uint8_t nal_header_size = offset ? 3 : 4;
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    *poutbuf_size += sps_pps_size+in_size+nal_header_size;
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    *poutbuf = av_realloc(*poutbuf, *poutbuf_size);
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    if (sps_pps)
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        memcpy(*poutbuf+offset, sps_pps, sps_pps_size);
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    memcpy(*poutbuf+sps_pps_size+nal_header_size+offset, in, in_size);
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    if (!offset)
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        AV_WB32(*poutbuf+sps_pps_size, 1);
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    else {
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        (*poutbuf+offset+sps_pps_size)[0] = (*poutbuf+offset+sps_pps_size)[1] = 0;
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        (*poutbuf+offset+sps_pps_size)[2] = 1;
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    }
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}
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static int h264_mp4toannexb_filter(AVBitStreamFilterContext *bsfc,
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                                   AVCodecContext *avctx, const char *args,
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                                   uint8_t  **poutbuf, int *poutbuf_size,
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                                   const uint8_t *buf, int      buf_size,
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                                   int keyframe) {
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    H264BSFContext *ctx = bsfc->priv_data;
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    uint8_t unit_type;
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    int32_t nal_size;
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    uint32_t cumul_size = 0;
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    const uint8_t *buf_end = buf + buf_size;
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    /* nothing to filter */
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    if (!avctx->extradata || avctx->extradata_size < 6) {
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        *poutbuf = (uint8_t*) buf;
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        *poutbuf_size = buf_size;
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        return 0;
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    }
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    /* retrieve sps and pps NAL units from extradata */
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    if (!ctx->extradata_parsed) {
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        uint16_t unit_size;
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        uint64_t total_size = 0;
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        uint8_t *out = NULL, unit_nb, sps_done = 0;
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        const uint8_t *extradata = avctx->extradata+4;
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        static const uint8_t nalu_header[4] = {0, 0, 0, 1};
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        /* retrieve length coded size */
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        ctx->length_size = (*extradata++ & 0x3) + 1;
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        if (ctx->length_size == 3)
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            return AVERROR(EINVAL);
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        /* retrieve sps and pps unit(s) */
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        unit_nb = *extradata++ & 0x1f; /* number of sps unit(s) */
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        if (!unit_nb) {
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            unit_nb = *extradata++; /* number of pps unit(s) */
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            sps_done++;
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        }
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        while (unit_nb--) {
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            unit_size = AV_RB16(extradata);
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            total_size += unit_size+4;
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            if (total_size > INT_MAX - FF_INPUT_BUFFER_PADDING_SIZE || extradata+2+unit_size > avctx->extradata+avctx->extradata_size) {
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                av_free(out);
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                return AVERROR(EINVAL);
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            }
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            out = av_realloc(out, total_size + FF_INPUT_BUFFER_PADDING_SIZE);
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            if (!out)
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                return AVERROR(ENOMEM);
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            memcpy(out+total_size-unit_size-4, nalu_header, 4);
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            memcpy(out+total_size-unit_size,   extradata+2, unit_size);
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            extradata += 2+unit_size;
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            if (!unit_nb && !sps_done++)
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                unit_nb = *extradata++; /* number of pps unit(s) */
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        }
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        memset(out + total_size, 0, FF_INPUT_BUFFER_PADDING_SIZE);
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        av_free(avctx->extradata);
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        avctx->extradata      = out;
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        avctx->extradata_size = total_size;
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        ctx->first_idr        = 1;
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        ctx->extradata_parsed = 1;
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    }
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    *poutbuf_size = 0;
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    *poutbuf = NULL;
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    do {
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        if (buf + ctx->length_size > buf_end)
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            goto fail;
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        if (ctx->length_size == 1)
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            nal_size = buf[0];
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        else if (ctx->length_size == 2)
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            nal_size = AV_RB16(buf);
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        else
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            nal_size = AV_RB32(buf);
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        buf += ctx->length_size;
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        unit_type = *buf & 0x1f;
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        if (buf + nal_size > buf_end || nal_size < 0)
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            goto fail;
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        /* prepend only to the first type 5 NAL unit of an IDR picture */
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        if (ctx->first_idr && unit_type == 5) {
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            alloc_and_copy(poutbuf, poutbuf_size,
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                           avctx->extradata, avctx->extradata_size,
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                           buf, nal_size);
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            ctx->first_idr = 0;
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        }
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        else {
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            alloc_and_copy(poutbuf, poutbuf_size,
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                           NULL, 0,
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                           buf, nal_size);
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            if (!ctx->first_idr && unit_type == 1)
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                ctx->first_idr = 1;
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        }
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        buf += nal_size;
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        cumul_size += nal_size + ctx->length_size;
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    } while (cumul_size < buf_size);
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    return 1;
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fail:
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    av_freep(poutbuf);
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    *poutbuf_size = 0;
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    return AVERROR(EINVAL);
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}
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AVBitStreamFilter h264_mp4toannexb_bsf = {
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    "h264_mp4toannexb",
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    sizeof(H264BSFContext),
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    h264_mp4toannexb_filter,
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};
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