static int read_interval_packets(WriterContext *w, InputFile *ifile,
                                 const ReadInterval *interval, int64_t *cur_ts)
{
    AVFormatContext *fmt_ctx = ifile->fmt_ctx;
    AVPacket pkt;
    AVFrame *frame = NULL;
    int ret = 0, i = 0, frame_count = 0;
    int64_t start = -INT64_MAX, end = interval->end;
    int has_start = 0, has_end = interval->has_end && !interval->end_is_offset;

    av_init_packet(&pkt);

    av_log(NULL, AV_LOG_VERBOSE, "Processing read interval ");
    log_read_interval(interval, NULL, AV_LOG_VERBOSE);

    if (interval->has_start) {
        int64_t target;
        if (interval->start_is_offset) {
            if (*cur_ts == AV_NOPTS_VALUE) {
                av_log(NULL, AV_LOG_ERROR,
                       "Could not seek to relative position since current "
                       "timestamp is not defined\n");
                ret = AVERROR(EINVAL);
                goto end;
            }
            target = *cur_ts + interval->start;
        } else {
            target = interval->start;
        }

        av_log(NULL, AV_LOG_VERBOSE, "Seeking to read interval start point %s\n",
               av_ts2timestr(target, &AV_TIME_BASE_Q));
        if ((ret = avformat_seek_file(fmt_ctx, -1, -INT64_MAX, target, INT64_MAX, 0)) < 0) {
            av_log(NULL, AV_LOG_ERROR, "Could not seek to position %"PRId64": %s\n",
                   interval->start, av_err2str(ret));
            goto end;
        }
    }

    frame = av_frame_alloc();
    if (!frame) {
        ret = AVERROR(ENOMEM);
        goto end;
    }
    while (!av_read_frame(fmt_ctx, &pkt)) {
        if (ifile->nb_streams > nb_streams) {
            REALLOCZ_ARRAY_STREAM(nb_streams_frames,  nb_streams, fmt_ctx->nb_streams);
            REALLOCZ_ARRAY_STREAM(nb_streams_packets, nb_streams, fmt_ctx->nb_streams);
            REALLOCZ_ARRAY_STREAM(selected_streams,   nb_streams, fmt_ctx->nb_streams);
            nb_streams = ifile->nb_streams;
        }
        if (selected_streams[pkt.stream_index]) {
            AVRational tb = ifile->streams[pkt.stream_index].st->time_base;

            if (pkt.pts != AV_NOPTS_VALUE)
                *cur_ts = av_rescale_q(pkt.pts, tb, AV_TIME_BASE_Q);

            if (!has_start && *cur_ts != AV_NOPTS_VALUE) {
                start = *cur_ts;
                has_start = 1;
            }

            if (has_start && !has_end && interval->end_is_offset) {
                end = start + interval->end;
                has_end = 1;
            }

            if (interval->end_is_offset && interval->duration_frames) {
                if (frame_count >= interval->end)
                    break;
            } else if (has_end && *cur_ts != AV_NOPTS_VALUE && *cur_ts >= end) {
                break;
            }

            frame_count++;
            if (do_read_packets) {
                if (do_show_packets)
                    show_packet(w, ifile, &pkt, i++);
                nb_streams_packets[pkt.stream_index]++;
            }
            if (do_read_frames) {
                int packet_new = 1;
                while (process_frame(w, ifile, frame, &pkt, &packet_new) > 0);
            }
        }
        av_packet_unref(&pkt);
    }
    av_init_packet(&pkt);
    pkt.data = NULL;
    pkt.size = 0;
    //Flush remaining frames that are cached in the decoder
    for (i = 0; i < fmt_ctx->nb_streams; i++) {
        pkt.stream_index = i;
        if (do_read_frames)
            while (process_frame(w, ifile, frame, &pkt, &(int){1}) > 0);
    }

end:
    av_frame_free(&frame);
    if (ret < 0) {
        av_log(NULL, AV_LOG_ERROR, "Could not read packets in interval ");
        log_read_interval(interval, NULL, AV_LOG_ERROR);
    }
    return ret;
}
static int read_interval_packets(WriterContext *w, InputFile *ifile,
                                 const ReadInterval *interval, int64_t *cur_ts)
{
    AVFormatContext *fmt_ctx = ifile->fmt_ctx;
    AVPacket pkt;
    AVFrame *frame = NULL;
    int ret = 0, i = 0, frame_count = 0;
    int64_t start = -INT64_MAX, end = interval->end;
    int has_start = 0, has_end = interval->has_end && !interval->end_is_offset;

    av_init_packet(&pkt);

    av_log(NULL, AV_LOG_VERBOSE, "Processing read interval ");
    log_read_interval(interval, NULL, AV_LOG_VERBOSE);

    if (interval->has_start) {
        int64_t target;
        if (interval->start_is_offset) {
            if (*cur_ts == AV_NOPTS_VALUE) {
                av_log(NULL, AV_LOG_ERROR,
                       "Could not seek to relative position since current "
                       "timestamp is not defined\n");
                ret = AVERROR(EINVAL);
                goto end;
            }
            target = *cur_ts + interval->start;
        } else {
            target = interval->start;
        }

        av_log(NULL, AV_LOG_VERBOSE, "Seeking to read interval start point %s\n",
               av_ts2timestr(target, &AV_TIME_BASE_Q));
        if ((ret = avformat_seek_file(fmt_ctx, -1, -INT64_MAX, target, INT64_MAX, 0)) < 0) {
            av_log(NULL, AV_LOG_ERROR, "Could not seek to position %"PRId64": %s\n",
                   interval->start, av_err2str(ret));
            goto end;
        }
    }

    frame = av_frame_alloc();
    if (!frame) {
        ret = AVERROR(ENOMEM);
        goto end;
    }
    while (!av_read_frame(fmt_ctx, &pkt)) {
        if (ifile->nb_streams > nb_streams) {
            REALLOCZ_ARRAY_STREAM(nb_streams_frames,  nb_streams, fmt_ctx->nb_streams);
            REALLOCZ_ARRAY_STREAM(nb_streams_packets, nb_streams, fmt_ctx->nb_streams);
            REALLOCZ_ARRAY_STREAM(selected_streams,   nb_streams, fmt_ctx->nb_streams);
            nb_streams = ifile->nb_streams;
        }
        if (selected_streams[pkt.stream_index]) {
            AVRational tb = ifile->streams[pkt.stream_index].st->time_base;

            if (pkt.pts != AV_NOPTS_VALUE)
                *cur_ts = av_rescale_q(pkt.pts, tb, AV_TIME_BASE_Q);

            if (!has_start && *cur_ts != AV_NOPTS_VALUE) {
                start = *cur_ts;
                has_start = 1;
            }

            if (has_start && !has_end && interval->end_is_offset) {
                end = start + interval->end;
                has_end = 1;
            }

            if (interval->end_is_offset && interval->duration_frames) {
                if (frame_count >= interval->end)
                    break;
            } else if (has_end && *cur_ts != AV_NOPTS_VALUE && *cur_ts >= end) {
                break;
            }

            frame_count++;
            if (do_read_packets) {
                if (do_show_packets)
                    show_packet(w, ifile, &pkt, i++);
                nb_streams_packets[pkt.stream_index]++;
            }
            if (do_read_frames) {
                int packet_new = 1;
                while (process_frame(w, ifile, frame, &pkt, &packet_new) > 0);
            }
        }
        av_packet_unref(&pkt);
    }
    av_init_packet(&pkt);
    pkt.data = NULL;
    pkt.size = 0;
     
    for (i = 0; i < fmt_ctx->nb_streams; i++) {
        pkt.stream_index = i;
        if (do_read_frames)
            while (process_frame(w, ifile, frame, &pkt, &(int){1}) > 0);
    }

end:
    av_frame_free(&frame);
    if (ret < 0) {
        av_log(NULL, AV_LOG_ERROR, "Could not read packets in interval ");
        log_read_interval(interval, NULL, AV_LOG_ERROR);
    }
    return ret;
}