decode.c

#include <stdio.h>
#include <libavformat/avformat.h>
#include <libavcodec/avcodec.h>

static AVFormatContext *inctx, *outctx;
#define MAX_STREAMS 16
static AVCodecContext *inavctx[MAX_STREAMS];
static AVCodecContext *outavctx[MAX_STREAMS];

static int openInputFile(const char *file) {
    int res;

    inctx = NULL;
    res = avformat_open_input(&inctx, file, NULL, NULL);
    if (res != 0)
        return res;
    res = avformat_find_stream_info(inctx, NULL);
    if (res < 0)
        return res;

    return 0;
}

static void closeInputFile(void) {
    int n;

    for (n = 0; n < inctx->nb_streams; n++)
        if (inavctx[n]) {
            avcodec_close(inavctx[n]);
            //avcodec_free_context(&inavctx[n]);
        }

    avformat_close_input(&inctx);
}

int main(int argc, char *argv[]) {
    char *input = argv[1];
    char *output = argv[2];
    int res;

    printf("Converting %s to %s\n", input, output);
    av_register_all();
    if ((res = openInputFile(input)) < 0) {
        fprintf(stderr, "Failed to open input file %s\n", input);
        return res;
    }

    AVFrame *frame = av_frame_alloc();
    AVPacket pkt;

    int videoStreamIndex = -1;

    for (int i = 0; i < inctx->nb_streams; i++) {
        AVStream *inst = inctx->streams[i];
        AVCodecContext *inc = inst->codec;

        if (inctx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO) {
            videoStreamIndex = i;
            inavctx[i] = avcodec_alloc_context3(inc->codec);
            avcodec_copy_context(inavctx[i], inc);
            if ((res = avcodec_open2(inavctx[i], avcodec_find_decoder(inc->codec_id), NULL)) < 0)
                return res;
            break;
        }
    }

    if (videoStreamIndex == -1) {
        printf("Could not find video stream\n");
        return -1;
    }

    av_init_packet(&pkt);
    uint64_t frameCount = 0;
    int keyFrame = 0;
    uint64_t lastIFramePos = 0;
    uint64_t lastIFramePts = 0;
    uint64_t lastIFrameCount = 0;
    uint64_t packetCount = 0;
    int frameFinished = 0;
    int codedPictureNumber = -1;
    int displayPictureNumber = -1;
    char pict_type;
    while (av_read_frame(inctx, &pkt) >= 0) {
        packetCount++;
        if (pkt.flags & AV_PKT_FLAG_CORRUPT) {
            printf("Corrupt packet detected! pos=%lu\n", pkt.pos);
        }
        if (pkt.stream_index == videoStreamIndex) {
                keyFrame = pkt.flags & AV_PKT_FLAG_KEY;
                res = avcodec_decode_video2(inavctx[videoStreamIndex],frame,&frameFinished,&pkt);
                if(frameFinished == 1) {
                     frameCount++;
                     codedPictureNumber = frame->coded_picture_number;
                     displayPictureNumber = frame->display_picture_number;
                     pict_type = av_get_picture_type_char(frame->pict_type);
                     if(frame->key_frame != keyFrame) {
                           printf("DIFF frame=%lu key_frame=%d frame->key_frame=%d pict_type=%c byte_pos=%lu pts=%lu packet=%lu poc=%d\n", frameCount,
                           keyFrame, frame->key_frame, pict_type, pkt.pos, pkt.pts, packetCount, codedPictureNumber);
                     }
                } else {
                     //pict_type = ' ';
                     //codedPictureNumber = 0;
                     //displayPictureNumber = 0;
                }
                if(res == -1) {
                     printf("Failed to decode video frame\n");
                     return -1;
                } 
            if (keyFrame == 1) {
                lastIFramePos = pkt.pos;
                lastIFramePts = pkt.pts;
                lastIFrameCount = frameCount;

            } else {
                if (pkt.pos > lastIFramePos && pkt.pts < lastIFramePts) {
                    printf("Open GOP detected! frame=%lu pos=%lu > "
                           "iframe_pos=%lu but "
                           "pts=%lu < iframe_pts=%lu\n",
                           frameCount, pkt.pos, lastIFramePos, pkt.pts,
                           lastIFramePts);
                }
            }
            printf("frame=%lu key_frame=%d pict_type=%c byte_pos=%lu pts=%lu packet=%lu poc=%d doc=%d\n", frameCount,
                   keyFrame, pict_type, pkt.pos, pkt.pts, packetCount, codedPictureNumber, displayPictureNumber);
        }
    }

    av_free_packet(&pkt);

    closeInputFile();

    return 0;
}