save AVPacket from mem to disk and then read back

save_packet_to_disk

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

static FILE *open_file_write(const char *file);
static FILE *open_file_read(const char *file);
static size_t write_packt_to_file(AVPacket *packet, FILE *file);
static size_t read_packt_from_file(AVPacket *packet, FILE *file);
static void close_file(FILE *file);

static void log_packet(const AVFormatContext *fmt_ctx, const AVPacket *pkt, const char *tag)
{
//    AVRational *time_base = &fmt_ctx->streams[pkt->stream_index]->time_base;

//    printf("%s: pts:%s pts_time:%s dts:%s dts_time:%s duration:%s duration_time:%s stream_index:%d\n",
//           tag,
//           av_ts2str(pkt->pts), av_ts2timestr(pkt->pts, time_base),
//           av_ts2str(pkt->dts), av_ts2timestr(pkt->dts, time_base),
//           av_ts2str(pkt->duration), av_ts2timestr(pkt->duration, time_base),
//           pkt->stream_index);
}
static void ff_log_callback(void*avcl, int level, const char*fmt, va_list vl)
{
    printf(fmt, vl);
}

int main(int argc, char **argv)
{
    AVOutputFormat *ofmt = NULL;
    AVFormatContext *ifmt_ctx = NULL, *ofmt_ctx = NULL;
    AVPacket pkt;
    AVPacket read_packet;
    const char *in_filename, *out_filename;
    int ret, i;

    if (argc < 3) {
        printf("usage: %s input output\n"
               "API example program to remux a media file with libavformat and libavcodec.\n"
               "The output format is guessed according to the file extension.\n"
               "\n", argv[0]);
        return 1;
    }

    in_filename  = argv[1];
    out_filename = argv[2];

    av_register_all();

    if ((ret = avformat_open_input(&ifmt_ctx, in_filename, 0, 0)) < 0) {
        fprintf(stderr, "Could not open input file '%s'", in_filename);
        goto end;
    }

    if ((ret = avformat_find_stream_info(ifmt_ctx, 0)) < 0) {
        fprintf(stderr, "Failed to retrieve input stream information");
        goto end;
    }

    av_log_set_level(48);
    av_log_set_callback(ff_log_callback);

    av_dump_format(ifmt_ctx, 0, in_filename, 0);

    avformat_alloc_output_context2(&ofmt_ctx, NULL, NULL, out_filename);
    if (!ofmt_ctx) {
        fprintf(stderr, "Could not create output context\n");
        ret = AVERROR_UNKNOWN;
        goto end;
    }

    ofmt = ofmt_ctx->oformat;

    for (i = 0; i < ifmt_ctx->nb_streams; i++) {
        AVStream *in_stream = ifmt_ctx->streams[i];
        AVStream *out_stream = avformat_new_stream(ofmt_ctx, in_stream->codec->codec);
        if (!out_stream) {
            fprintf(stderr, "Failed allocating output stream\n");
            ret = AVERROR_UNKNOWN;
            goto end;
        }

        ret = avcodec_copy_context(out_stream->codec, in_stream->codec);
        if (ret < 0) {
            fprintf(stderr, "Failed to copy context from input to output stream codec context\n");
            goto end;
        }
        out_stream->codec->codec_tag = 0;
        if (ofmt_ctx->oformat->flags & AVFMT_GLOBALHEADER)
            out_stream->codec->flags |= CODEC_FLAG_GLOBAL_HEADER;
    }
    av_dump_format(ofmt_ctx, 0, out_filename, 1);

    if (!(ofmt->flags & AVFMT_NOFILE)) {
        ret = avio_open(&ofmt_ctx->pb, out_filename, AVIO_FLAG_WRITE);
        if (ret < 0) {
            fprintf(stderr, "Could not open output file '%s'", out_filename);
            goto end;
        }
    }

    ret = avformat_write_header(ofmt_ctx, NULL);
    if (ret < 0) {
        fprintf(stderr, "Error occurred when opening output file\n");
        goto end;
    }

    FILE *file_write = open_file_write("/Users/sunjun/Desktop/packt_file.b");
    FILE *file_read = open_file_read("/Users/sunjun/Desktop/packt_file.b");
    while (1) {
        AVStream *in_stream, *out_stream;

        ret = av_read_frame(ifmt_ctx, &pkt);
        if (ret < 0)
            break;


        write_packt_to_file(&pkt, file_write);
        read_packt_from_file(&read_packet, file_read);
        
        in_stream  = ifmt_ctx->streams[read_packet.stream_index];
        out_stream = ofmt_ctx->streams[read_packet.stream_index];

        log_packet(ifmt_ctx, &read_packet, "in");

        /* copy packet */
        read_packet.pts = av_rescale_q_rnd(read_packet.pts, in_stream->time_base, out_stream->time_base, AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX);
        read_packet.dts = av_rescale_q_rnd(read_packet.dts, in_stream->time_base, out_stream->time_base, AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX);
        read_packet.duration = (int)av_rescale_q(read_packet.duration, in_stream->time_base, out_stream->time_base);
        read_packet.pos = -1;
        log_packet(ofmt_ctx, &read_packet, "out");
        
        //写音频流的packet时候会出错
        ret = av_interleaved_write_frame(ofmt_ctx, &read_packet);
        if (ret < 0) {
            fprintf(stderr, "Error muxing packet\n");
            break;
        }
        av_free_packet(&read_packet);
        av_free_packet(&pkt);
    }
    
    av_write_trailer(ofmt_ctx);
    close_file(file_write);
    close_file(file_read);
end:

    avformat_close_input(&ifmt_ctx);

    /* close output */
    if (ofmt_ctx && !(ofmt->flags & AVFMT_NOFILE))
        avio_closep(&ofmt_ctx->pb);
    avformat_free_context(ofmt_ctx);

    if (ret < 0 && ret != AVERROR_EOF) {
        fprintf(stderr, "Error occurred: %s\n", av_err2str(ret));
        return 1;
    }

    return 0;
}

static FILE *open_file_write(const char *file)
{
    FILE *packt_file = NULL;

    packt_file = fopen(file, "wb+");

    return packt_file;
}

static FILE *open_file_read(const char *file)
{
    FILE *packt_file = NULL;

    packt_file = fopen(file, "rb+");

    return packt_file;
}

static size_t read_packt_from_file(AVPacket *packet, FILE *file)
{
    size_t ret = 0;
    
    
    ret = fread(packet, sizeof(AVPacket), 1, file);
    packet->data = malloc(packet->size);
    ret = fread(packet->data, packet->size, 1, file);
    if (packet->buf) {
        int buf_size = packet->buf->size;
        packet->buf = malloc(sizeof(AVBufferRef));
        packet->buf->size = buf_size;
        packet->buf->data = malloc(packet->buf->size);
        ret = fread(packet->buf->data, packet->buf->size, 1, file);
    }
    return ret;
}

static size_t write_packt_to_file(AVPacket *packet, FILE *file)
{
    size_t ret = 0;
    ret = fwrite(packet, sizeof(AVPacket), 1, file);
    ret = fwrite(packet->data, packet->size, 1, file);
    if (packet->buf) {
        fwrite(packet->buf->data, packet->buf->size, 1, file);
    }
    fflush(file);
    return ret;
}

static void close_file(FILE *file)
{
    fclose(file);
}