PeerStreamer

/*

 * 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 "libavutil/intreadwrite.h"

#include "avcodec.h"

typedef struct H264BSFContext {

    uint8_t  length_size;

    uint8_t  first_idr;

    uint8_t *sps_pps_data;

    uint32_t size;

} H264BSFContext;

static void 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;

    *poutbuf_size += sps_pps_size+in_size+nal_header_size;

    *poutbuf = av_realloc(*poutbuf, *poutbuf_size);

    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;

    }

}

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;

    uint8_t unit_type;

    int32_t nal_size;

    uint32_t cumul_size = 0;

    const uint8_t *buf_end = buf + buf_size;

    /* 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->sps_pps_data) {

        uint16_t unit_size;

        uint32_t total_size = 0;

        uint8_t *out = NULL, unit_nb, sps_done = 0;

        const uint8_t *extradata = avctx->extradata+4;

        static const uint8_t nalu_header[4] = {0, 0, 0, 1};

        /* retrieve length coded size */

        ctx->length_size = (*extradata++ & 0x3) + 1;

        if (ctx->length_size == 3)

            return AVERROR(EINVAL);

        /* retrieve sps and pps unit(s) */

        unit_nb = *extradata++ & 0x1f; /* number of sps unit(s) */

        if (!unit_nb) {

            unit_nb = *extradata++; /* number of pps unit(s) */

            sps_done++;

        }

        while (unit_nb--) {

            unit_size = AV_RB16(extradata);

            total_size += unit_size+4;

            if (extradata+2+unit_size > avctx->extradata+avctx->extradata_size) {

                av_free(out);

                return AVERROR(EINVAL);

            }

            out = av_realloc(out, total_size);

            if (!out)

                return AVERROR(ENOMEM);

            memcpy(out+total_size-unit_size-4, nalu_header, 4);

            memcpy(out+total_size-unit_size,   extradata+2, unit_size);

            extradata += 2+unit_size;

            if (!unit_nb && !sps_done++)

                unit_nb = *extradata++; /* number of pps unit(s) */

        }

        ctx->sps_pps_data = out;

        ctx->size = total_size;

        ctx->first_idr = 1;

    }

    *poutbuf_size = 0;

    *poutbuf = NULL;

    do {

        if (buf + ctx->length_size > buf_end)

            goto fail;

        if (ctx->length_size == 1)

            nal_size = buf[0];

        else if (ctx->length_size == 2)

            nal_size = AV_RB16(buf);

        else

            nal_size = AV_RB32(buf);

        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) {

            alloc_and_copy(poutbuf, poutbuf_size,

                           ctx->sps_pps_data, ctx->size,

                           buf, nal_size);

            ctx->first_idr = 0;

        }

        else {

            alloc_and_copy(poutbuf, poutbuf_size,

                           NULL, 0,

                           buf, nal_size);

            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 AVERROR(EINVAL);

}

static void h264_mp4toannexb_close(AVBitStreamFilterContext *bsfc)

{

    H264BSFContext *ctx = bsfc->priv_data;

    av_freep(&ctx->sps_pps_data);

}

AVBitStreamFilter h264_mp4toannexb_bsf = {

    "h264_mp4toannexb",

    sizeof(H264BSFContext),

    h264_mp4toannexb_filter,

    h264_mp4toannexb_close,

};