demuxing media file

demuxing.c

#include <libavutil/imgutils.h>
#include <libavutil/samplefmt.h>
#include <libavutil/timestamp.h>
#include <libavformat/avformat.h>

static AVFormatContext *fmt_ctx = NULL;
static AVCodecContext *video_dec_ctx = NULL, *audio_dec_ctx;
static AVStream *video_stream = NULL, *audio_stream = NULL;
static const char *src_filename = NULL;

static uint8_t *video_dst_data[4] = {NULL};
static int      video_dst_linesize[4];
static int video_dst_bufsize;

static uint8_t **audio_dst_data = NULL;
static int       audio_dst_linesize;
static int audio_dst_bufsize;

static int video_stream_idx = -1, audio_stream_idx = -1;
static AVPacket pkt;
static int video_frame_count = 0;
static int audio_frame_count = 0;

static int decode_packet(int *got_frame, int cached)
{
    int ret = 0;

    if (pkt.stream_index == video_stream_idx) {
        // TODO 检查是否x264 params string
        printf("Video pkt size: %i, data: %x %x %x %x %x %x %x %x\n",
                pkt.size,
                pkt.data[0], pkt.data[1], pkt.data[2], pkt.data[3],
                pkt.data[4], pkt.data[5], pkt.data[6], pkt.data[7]);
    }

    return ret;
}

static int open_codec_context(int *stream_idx,
                              AVFormatContext *fmt_ctx, enum AVMediaType type)
{
    int ret;

    ret = av_find_best_stream(fmt_ctx, type, -1, -1, NULL, 0);
    if (ret < 0) {
        fprintf(stderr, "Could not find %s stream in input file '%s'\n",
                av_get_media_type_string(type), src_filename);
        return ret;
    }
    *stream_idx = ret;

    return 0;
}

static int get_format_from_sample_fmt(const char **fmt,
                                      enum AVSampleFormat sample_fmt)
{
    int i;
    struct sample_fmt_entry {
        enum AVSampleFormat sample_fmt; const char *fmt_be, *fmt_le;
    } sample_fmt_entries[] = {
        { AV_SAMPLE_FMT_U8,  "u8",    "u8"    },
        { AV_SAMPLE_FMT_S16, "s16be", "s16le" },
        { AV_SAMPLE_FMT_S32, "s32be", "s32le" },
        { AV_SAMPLE_FMT_FLT, "f32be", "f32le" },
        { AV_SAMPLE_FMT_DBL, "f64be", "f64le" },
    };
    *fmt = NULL;

    for (i = 0; i < FF_ARRAY_ELEMS(sample_fmt_entries); i++) {
        struct sample_fmt_entry *entry = &sample_fmt_entries[i];
        if (sample_fmt == entry->sample_fmt) {
            *fmt = AV_NE(entry->fmt_be, entry->fmt_le);
            return 0;
        }
    }

    fprintf(stderr,
            "sample format %s is not supported as output format\n",
            av_get_sample_fmt_name(sample_fmt));
    return -1;
}

int main (int argc, char **argv)
{
    int ret = 0, got_frame;
    
    if(argc < 2){
        printf("Need filename.\n");
        return -1;
    }

    src_filename = argv[1];

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

    /* open input file, and allocate format context */
    if (avformat_open_input(&fmt_ctx, src_filename, NULL, NULL) < 0) {
        fprintf(stderr, "Could not open source file %s\n", src_filename);
        exit(1);
    }
    printf("After open input file.\n");

    /* retrieve stream information */
    if (avformat_find_stream_info(fmt_ctx, NULL) < 0) {
        fprintf(stderr, "Could not find stream information\n");
        exit(1);
    }
    printf("After find stream info.\n");

    if (open_codec_context(&video_stream_idx, fmt_ctx, AVMEDIA_TYPE_VIDEO) >= 0) {
        video_stream = fmt_ctx->streams[video_stream_idx];
        video_dec_ctx = video_stream->codec;
    }
    printf("After open video codec context.\n");

    if (open_codec_context(&audio_stream_idx, fmt_ctx, AVMEDIA_TYPE_AUDIO) >= 0) {
        audio_stream = fmt_ctx->streams[audio_stream_idx];
        audio_dec_ctx = audio_stream->codec;
    }
    printf("After open audio codec context.\n");

    /* dump input information to stderr */
    av_dump_format(fmt_ctx, 0, src_filename, 0);
    printf("After dump format.\n");

    if (!audio_stream && !video_stream) {
        fprintf(stderr, "Could not find audio or video stream in the input, aborting\n");
        ret = 1;
        goto end;
    }

    /* initialize packet, set data to NULL, let the demuxer fill it */
    av_init_packet(&pkt);
    pkt.data = NULL;
    pkt.size = 0;

    /* read frames from the file */
    while (av_read_frame(fmt_ctx, &pkt) >= 0)
        decode_packet(&got_frame, 0);

    /* flush cached frames */
    pkt.data = NULL;
    pkt.size = 0;
    do {
        decode_packet(&got_frame, 1);
    } while (got_frame);

    printf("Demuxing succeeded.\n");

end:
    if (video_dec_ctx)
        avcodec_close(video_dec_ctx);
    if (audio_dec_ctx)
        avcodec_close(audio_dec_ctx);
    avformat_close_input(&fmt_ctx);

    return ret < 0;
}