Quick-and-dirty documentation for libvo from libmpeg2 0.3.1
Kees Cook <mpeg2@outflux.net>
2003-04-17



Basic Usage Pseudocode
----------------------

vo_driver_t *     drivers     = NULL;
vo_open_t *       output_open = NULL;
vo_instance_t *   output      = NULL;
vo_setup_result_t setup_result;

/* find the desired driver */
drivers = vo_drivers();
for (i = 0; drivers && drivers[i].name != NULL; i++) {
        if (this is the one you want) {
                output_open = drivers[i].open;
                break; 
        }
}
if (!output_open) {
        blow up: no valid output found
}

/* open the output driver */
if (!(output = output_open())) {
        blow up: instance failed to initialize
}


/* start up decoder */
mpeg2dec=mpeg2_init();

while (data) {        
        const mpeg2_info_t * info;

        get some data

        mpeg2_buffer(mpeg2dec,data_start,data_end);
        info=mpeg2_info(mpeg2dec);
        switch (mpeg2_parse(mpeg2dec)) {
        case -1:
            /* needs more data */
            continue;
        case STATE_SEQUENCE:
            /* sequence started, so initialize output window */
            if (output->setup (output, info->sequence->width,
                               info->sequence->height, &setup_result)) {
                fprintf (stderr, "display setup failed\n");
                exit (1);
            }
            /* does the output need to be converted? */
            if (setup_result.convert)
                mpeg2_convert (mpeg2dec, setup_result.convert, NULL);
            /* can the output provide an fbuf area? */
            if (output->set_fbuf) {
                uint8_t * buf[3];
                void * id;

                mpeg2_custom_fbuf (mpeg2dec, 1);
                output->set_fbuf (output, buf, &id);
                mpeg2_set_buf (mpeg2dec, buf, id);
                output->set_fbuf (output, buf, &id);
                mpeg2_set_buf (mpeg2dec, buf, id);
            } else if (output->setup_fbuf) {
                uint8_t * buf[3];
                void * id;

                output->setup_fbuf (output, buf, &id);
                mpeg2_set_buf (mpeg2dec, buf, id);
                output->setup_fbuf (output, buf, &id);
                mpeg2_set_buf (mpeg2dec, buf, id);
                output->setup_fbuf (output, buf, &id);
                mpeg2_set_buf (mpeg2dec, buf, id);
            }
            break;
        case STATE_PICTURE:
            /* picture is starting */
            if (output->set_fbuf) {
                uint8_t * buf[3];
                void * id;

                output->set_fbuf (output, buf, &id);
                mpeg2_set_buf (mpeg2dec, buf, id);
            }
            if (output->start_fbuf)
                output->start_fbuf (output, info->current_fbuf->buf,
                                    info->current_fbuf->id);
            break;
        case STATE_SLICE:
        case STATE_END:
            /* draw current picture */
            if (info->display_fbuf) {
                output->draw (output, info->display_fbuf->buf,
                              info->display_fbuf->id);
            }
            if (output->discard && info->discard_fbuf)
                output->discard (output, info->discard_fbuf->buf,
                                 info->discard_fbuf->id);
            break;
        }
}

/* shutdown decoder */
mpeg2_close(mpeg2dec);
mpeg2dec=NULL;

/* close output driver */
if (output && output->close) output->close(output);
output=NULL;