ffmpeg源码学习

ffmpeg.c

static int transcode(void)
{
    int ret, i;
    AVFormatContext *os;
    OutputStream *ost;
    InputStream *ist;
    int64_t timer_start;

    ret = transcode_init();
    if (ret < 0)
        goto fail;

    if (stdin_interaction) {
        av_log(NULL, AV_LOG_INFO, "Press [q] to stop, [?] for help
");
    }

    timer_start = av_gettime();

#if HAVE_PTHREADS
    if ((ret = init_input_threads()) < 0)
        goto fail;
#endif

    while (!received_sigterm) {
        int64_t cur_time= av_gettime();

        /* if 'q' pressed, exits */
        if (stdin_interaction)
            if (check_keyboard_interaction(cur_time) < 0)
                break;

        /* check if there's any stream where output is still needed */
        if (!need_output()) {
            av_log(NULL, AV_LOG_VERBOSE, "No more output streams to write to, finishing.
");
            break;
        }

        ret = transcode_step();
        if (ret < 0) {
            if (ret == AVERROR_EOF || ret == AVERROR(EAGAIN))
                continue;

            av_log(NULL, AV_LOG_ERROR, "Error while filtering.
");
            break;
        }

        /* dump report by using the output first video and audio streams */
        print_report(0, timer_start, cur_time);
    }
#if HAVE_PTHREADS
    free_input_threads();
#endif

    /* at the end of stream, we must flush the decoder buffers */
    for (i = 0; i < nb_input_streams; i++) {
        ist = input_streams[i];
        if (!input_files[ist->file_index]->eof_reached && ist->decoding_needed) {
            output_packet(ist, NULL);
        }
    }
    flush_encoders();

    term_exit();

    /* write the trailer if needed and close file */
    for (i = 0; i < nb_output_files; i++) {
        os = output_files[i]->ctx;
        av_write_trailer(os);
    }

    /* dump report by using the first video and audio streams */
    print_report(1, timer_start, av_gettime());

    /* close each encoder */
    for (i = 0; i < nb_output_streams; i++) {
        ost = output_streams[i];
        if (ost->encoding_needed) {
            av_freep(&ost->st->codec->stats_in);
            avcodec_close(ost->st->codec);
        }
    }

    /* close each decoder */
    for (i = 0; i < nb_input_streams; i++) {
        ist = input_streams[i];
        if (ist->decoding_needed) {
            avcodec_close(ist->st->codec);
        }
    }

    /* finished ! */
    ret = 0;

 fail:
#if HAVE_PTHREADS
    free_input_threads();
#endif

    if (output_streams) {
        for (i = 0; i < nb_output_streams; i++) {
            ost = output_streams[i];
            if (ost) {
                if (ost->stream_copy)
                    av_freep(&ost->st->codec->extradata);
                if (ost->logfile) {
                    fclose(ost->logfile);
                    ost->logfile = NULL;
                }
                av_freep(&ost->st->codec->subtitle_header);
                av_freep(&ost->forced_kf_pts);
                av_freep(&ost->apad);
                av_dict_free(&ost->opts);
                av_dict_free(&ost->swr_opts);
                av_dict_free(&ost->resample_opts);
            }
        }
    }
    return ret;
}

初始化

static int transcode(void)
{
    int ret, i;
    AVFormatContext *os;
    OutputStream *ost;
    InputStream *ist;
    int64_t timer_start;

    ret = transcode_init();
    if (ret < 0)
        goto fail;

    if (stdin_interaction) {
        av_log(NULL, AV_LOG_INFO, "Press [q] to stop, [?] for help
");
    }

    timer_start = av_gettime();

#if HAVE_PTHREADS
    if ((ret = init_input_threads()) < 0)
        goto fail;
#endif

    while (!received_sigterm) {
        int64_t cur_time= av_gettime();

        /* if 'q' pressed, exits */
        if (stdin_interaction)
            if (check_keyboard_interaction(cur_time) < 0)
                break;

        /* check if there's any stream where output is still needed */
        if (!need_output()) {
            av_log(NULL, AV_LOG_VERBOSE, "No more output streams to write to, finishing.
");
            break;
        }

        ret = transcode_step();
        if (ret < 0) {
            if (ret == AVERROR_EOF || ret == AVERROR(EAGAIN))
                continue;

            av_log(NULL, AV_LOG_ERROR, "Error while filtering.
");
            break;
        }

        /* dump report by using the output first video and audio streams */
        print_report(0, timer_start, cur_time);
    }
#if HAVE_PTHREADS
    free_input_threads();
#endif

    /* at the end of stream, we must flush the decoder buffers */
    for (i = 0; i < nb_input_streams; i++) {
        ist = input_streams[i];
        if (!input_files[ist->file_index]->eof_reached && ist->decoding_needed) {
            output_packet(ist, NULL);
        }
    }
    flush_encoders();

    term_exit();

    /* write the trailer if needed and close file */
    for (i = 0; i < nb_output_files; i++) {
        os = output_files[i]->ctx;
        av_write_trailer(os);
    }

    /* dump report by using the first video and audio streams */
    print_report(1, timer_start, av_gettime());

    /* close each encoder */
    for (i = 0; i < nb_output_streams; i++) {
        ost = output_streams[i];
        if (ost->encoding_needed) {
            av_freep(&ost->st->codec->stats_in);
            avcodec_close(ost->st->codec);
        }
    }

    /* close each decoder */
    for (i = 0; i < nb_input_streams; i++) {
        ist = input_streams[i];
        if (ist->decoding_needed) {
            avcodec_close(ist->st->codec);
        }
    }

    /* finished ! */
    ret = 0;

 fail:
#if HAVE_PTHREADS
    free_input_threads();
#endif

    if (output_streams) {
        for (i = 0; i < nb_output_streams; i++) {
            ost = output_streams[i];
            if (ost) {
                if (ost->stream_copy)
                    av_freep(&ost->st->codec->extradata);
                if (ost->logfile) {
                    fclose(ost->logfile);
                    ost->logfile = NULL;
                }
                av_freep(&ost->st->codec->subtitle_header);
                av_freep(&ost->forced_kf_pts);
                av_freep(&ost->apad);
                av_dict_free(&ost->opts);
                av_dict_free(&ost->swr_opts);
                av_dict_free(&ost->resample_opts);
            }
        }
    }
    return ret;
}