FFmpeg從流媒體文件中抽取出視頻

#include <stdio.h>
#include <libavutil/log.h>
#include <libavformat/avio.h>
#include <libavformat/avformat.h>


#ifndef AV_WB32
#   define AV_WB32(p, val) do {                 \
        uint32_t d = (val);                     \
        ((uint8_t*)(p))[3] = (d);               \
        ((uint8_t*)(p))[2] = (d)>>8;            \
        ((uint8_t*)(p))[1] = (d)>>16;           \
        ((uint8_t*)(p))[0] = (d)>>24;           \
    } while(0)
#endif

#ifndef AV_RB16
#   define AV_RB16(x)                           \
    ((((const uint8_t*)(x))[0] << 8) |          \
      ((const uint8_t*)(x))[1])
#endif

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 = 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;
}

int h264_extradata_to_annexb(const uint8_t *codec_extradata, const int codec_extradata_size, AVPacket *out_extradata, 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, sps_offset = 0, pps_offset = 0;
    const uint8_t *extradata            = codec_extradata + 4;
    static const uint8_t nalu_header[4] = { 0, 0, 0, 1 };
    int length_size = (*extradata++ & 0x3) + 1; // retrieve length coded size, 用於指示表示NALU數據長度所需佔用的字節數

    sps_offset = pps_offset = -1;

    /* retrieve sps and pps unit(s) */
    unit_nb = *extradata++ & 0x1f; /* number of sps unit(s) */
    if (!unit_nb) {
        goto pps;
    }else {
        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(NULL, 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 > codec_extradata + codec_extradata_size) {
            av_log(NULL, 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) {
                pps_offset = total_size;
                pps_seen = 1;
            }
        }
    }

    if (out)
        memset(out + total_size, 0, padding);

    if (!sps_seen)
        av_log(NULL, AV_LOG_WARNING,
               "Warning: SPS NALU missing or invalid. "
               "The resulting stream may not play.\n");

    if (!pps_seen)
        av_log(NULL, AV_LOG_WARNING,
               "Warning: PPS NALU missing or invalid. "
               "The resulting stream may not play.\n");

    out_extradata->data      = out;
    out_extradata->size      = total_size;

    return length_size;
}

int h264_mp4toannexb(AVFormatContext *fmt_ctx, AVPacket *in, FILE *dst_fd)
{

    AVPacket *out = NULL;
    AVPacket spspps_pkt;

    int len;
    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;

    out = av_packet_alloc();

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

    do {
        ret= AVERROR(EINVAL);
        if (buf + 4 /*s->length_size*/ > buf_end)
            goto fail;

        for (nal_size = 0, i = 0; i<4/*s->length_size*/; i++)
            nal_size = (nal_size << 8) | buf[i];

        buf += 4; /*s->length_size;*/
        unit_type = *buf & 0x1f;

        if (nal_size > buf_end - buf || nal_size < 0)
            goto fail;

        /* 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*/) {

            h264_extradata_to_annexb( fmt_ctx->streams[in->stream_index]->codec->extradata,
                                      fmt_ctx->streams[in->stream_index]->codec->extradata_size,
                                      &spspps_pkt,
                                      AV_INPUT_BUFFER_PADDING_SIZE);

            if ((ret=alloc_and_copy(out,
                                    spspps_pkt.data, spspps_pkt.size,
                                    buf, nal_size)) < 0)
                goto fail;
            /*s->new_idr = 0;*/
            /* if only SPS has been seen, also insert PPS */
        }
             else {
            if ((ret=alloc_and_copy(out, NULL, 0, buf, nal_size)) < 0)
                goto fail;
        }


        len = fwrite( out->data, 1, out->size, dst_fd);
        if(len != out->size){
            av_log(NULL, AV_LOG_DEBUG, "warning, length of writed data isn't equal pkt.size(%d, %d)\n",
                   len,
                   out->size);
        }
        fflush(dst_fd);

        buf        += nal_size;
        cumul_size += nal_size + 4;//s->length_size;
    } while (cumul_size < buf_size);

    fail:
    av_packet_free(&out);

    return ret;
}

int main(int argc, char *argv[])
{
    int err_code;
    char errors[1024];

    char *src_filename = NULL;
    char *dst_filename = NULL;

    FILE *dst_fd = NULL;

    int video_stream_index = -1;

    AVFormatContext *fmt_ctx = NULL;
    AVPacket pkt;

    av_log_set_level(AV_LOG_DEBUG);

    if(argc < 3){
        av_log(NULL, AV_LOG_DEBUG, "the count of parameters should be more than three!\n");
        return -1;
    }

    src_filename = argv[1];
    dst_filename = argv[2];

    if(src_filename == NULL || dst_filename == NULL){
        av_log(NULL, AV_LOG_ERROR, "src or dts file is null, plz check them!\n");
        return -1;
    }

    /*register all formats and codec*/
    av_register_all();

    dst_fd = fopen(dst_filename, "wb");
    if (!dst_fd) {
        av_log(NULL, AV_LOG_DEBUG, "Could not open destination file %s\n", dst_filename);
        return -1;
    }

    /*open input media file, and allocate format context*/
    if((err_code = avformat_open_input(&fmt_ctx, src_filename, NULL, NULL)) < 0){
        av_strerror(err_code, errors, 1024);
        av_log(NULL, AV_LOG_DEBUG, "Could not open source file: %s, %d(%s)\n",
               src_filename,
               err_code,
               errors);
        return -1;
    }

    /*dump input information*/
    av_dump_format(fmt_ctx, 0, src_filename, 0);

    /*initialize packet*/
    av_init_packet(&pkt);
    pkt.data = NULL;
    pkt.size = 0;

    /*find best video stream*/
    video_stream_index = av_find_best_stream(fmt_ctx, AVMEDIA_TYPE_VIDEO, -1, -1, NULL, 0);
    if(video_stream_index < 0){
        av_log(NULL, AV_LOG_DEBUG, "Could not find %s stream in input file %s\n",
               av_get_media_type_string(AVMEDIA_TYPE_VIDEO),
               src_filename);
        return AVERROR(EINVAL);
    }

    /*read frames from media file*/
    while(av_read_frame(fmt_ctx, &pkt) >=0 ){
        if(pkt.stream_index == video_stream_index){
            /*
            pkt.stream_index = 0;
            av_write_frame(ofmt_ctx, &pkt);
            av_free_packet(&pkt);
            */

            h264_mp4toannexb(fmt_ctx, &pkt, dst_fd);

        }

        //release pkt->data
        av_packet_unref(&pkt);
    }

    //av_write_trailer(ofmt_ctx);

    /*close input media file*/
    avformat_close_input(&fmt_ctx);
    if(dst_fd) {
        fclose(dst_fd);
    }

    return 0;
}