opengl_enc.c

    OpenGLContext *opengl = h->priv_data;
    AVStream *st;
    int ret;

    if (h->nb_streams != 1 ||
        h->streams[0]->codec->codec_type != AVMEDIA_TYPE_VIDEO ||
        h->streams[0]->codec->codec_id != AV_CODEC_ID_RAWVIDEO) {
        av_log(opengl, AV_LOG_ERROR, "Only a single video stream is supported.\n");
        return AVERROR(EINVAL);
    }
    st = h->streams[0];
    opengl->width = st->codec->width;
    opengl->height = st->codec->height;
    opengl->pix_fmt = st->codec->pix_fmt;

    if (!opengl->window_title && !opengl->no_window)
        opengl->window_title = av_strdup(h->filename);

    if (!opengl->no_window) {
#if HAVE_SDL
        if ((ret = opengl_sdl_create_window(h)) < 0)
            goto fail;
#else
        av_log(opengl, AV_LOG_ERROR, "FFmpeg is compiled without SDL. Cannot create default window.\n");
        ret = AVERROR(ENOSYS);
        goto fail;
#endif
    } else {
        if ((ret = avdevice_dev_to_app_control_message(h, AV_DEV_TO_APP_CREATE_WINDOW_BUFFER, NULL , 0)) < 0) {
            av_log(opengl, AV_LOG_ERROR, "Application failed to create window buffer.\n");
            goto fail;
        }
        if ((ret = avdevice_dev_to_app_control_message(h, AV_DEV_TO_APP_PREPARE_WINDOW_BUFFER, NULL , 0)) < 0) {
            av_log(opengl, AV_LOG_ERROR, "Application failed to prepare window buffer.\n");
            goto fail;
        }
    }

    if ((ret = opengl_read_limits(opengl)) < 0)
        goto fail;

    if (opengl->width > opengl->max_texture_size || opengl->height > opengl->max_texture_size) {
        av_log(opengl, AV_LOG_ERROR, "Too big picture %dx%d, max supported size is %dx%d\n",
               opengl->width, opengl->height, opengl->max_texture_size, opengl->max_texture_size);
        ret = AVERROR(EINVAL);
        goto fail;
    }

    if (!opengl->no_window) {
#if HAVE_SDL
        if ((ret = opengl_sdl_load_procedures(opengl)) < 0)
            goto fail;
#endif
    } else if ((ret = opengl_load_procedures(opengl)) < 0)
        goto fail;

    opengl_fill_color_map(opengl);
    opengl_get_texture_params(opengl);

    if ((ret = opengl_init_context(opengl)) < 0)
        goto fail;

    if ((ret = opengl_prepare_vertex(h)) < 0)
        goto fail;

    glClear(GL_COLOR_BUFFER_BIT);

#if HAVE_SDL
    if (!opengl->no_window)
        SDL_GL_SwapBuffers();
#endif
    if (opengl->no_window &&
        (ret = avdevice_dev_to_app_control_message(h, AV_DEV_TO_APP_DISPLAY_WINDOW_BUFFER, NULL , 0)) < 0) {
        av_log(opengl, AV_LOG_ERROR, "Application failed to display window buffer.\n");
        goto fail;
    }

    ret = AVERROR_EXTERNAL;
    OPENGL_ERROR_CHECK(opengl);
    return 0;

  fail:
    opengl_write_trailer(h);
    return ret;
}

static uint8_t* opengl_get_plane_pointer(OpenGLContext *opengl, AVPacket *pkt, int comp_index,
                                         const AVPixFmtDescriptor *desc)
{
    uint8_t *data = pkt->data;
    int wordsize = opengl_type_size(opengl->type);
    int width_chroma = FF_CEIL_RSHIFT(opengl->width, desc->log2_chroma_w);
    int height_chroma = FF_CEIL_RSHIFT(opengl->height, desc->log2_chroma_h);
    int plane = desc->comp[comp_index].plane;

    switch(plane) {
    case 0:
        break;
    case 1:
        data += opengl->width * opengl->height * wordsize;
        break;
    case 2:
        data += opengl->width * opengl->height * wordsize;
        data += width_chroma * height_chroma * wordsize;
        break;
    case 3:
        data += opengl->width * opengl->height * wordsize;
        data += 2 * width_chroma * height_chroma * wordsize;
        break;
    default:
        return NULL;
    }
    return data;
}

static int opengl_draw(AVFormatContext *h, AVPacket *pkt, int repaint)
{
    OpenGLContext *opengl = h->priv_data;
    enum AVPixelFormat pix_fmt = h->streams[0]->codec->pix_fmt;
    const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(pix_fmt);
    int ret;

#if HAVE_SDL
    if (!opengl->no_window && (ret = opengl_sdl_process_events(h)) < 0)
        goto fail;
#endif
    if (opengl->no_window &&
        (ret = avdevice_dev_to_app_control_message(h, AV_DEV_TO_APP_PREPARE_WINDOW_BUFFER, NULL , 0)) < 0) {
        av_log(opengl, AV_LOG_ERROR, "Application failed to prepare window buffer.\n");
        goto fail;
    }

    glClear(GL_COLOR_BUFFER_BIT);

    if (!repaint) {
        glBindTexture(GL_TEXTURE_2D, opengl->texture_name[0]);
        glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, opengl->width, opengl->height, opengl->format, opengl->type,
                        opengl_get_plane_pointer(opengl, pkt, 0, desc));
        if (desc->flags & AV_PIX_FMT_FLAG_PLANAR) {
            int width_chroma = FF_CEIL_RSHIFT(opengl->width, desc->log2_chroma_w);
            int height_chroma = FF_CEIL_RSHIFT(opengl->height, desc->log2_chroma_h);
            glBindTexture(GL_TEXTURE_2D, opengl->texture_name[1]);
            glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, width_chroma, height_chroma, opengl->format, opengl->type,
                            opengl_get_plane_pointer(opengl, pkt, 1, desc));
            glBindTexture(GL_TEXTURE_2D, opengl->texture_name[2]);
            glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, width_chroma, height_chroma, opengl->format, opengl->type,
                            opengl_get_plane_pointer(opengl, pkt, 2, desc));
            if (desc->flags & AV_PIX_FMT_FLAG_ALPHA) {
                glBindTexture(GL_TEXTURE_2D, opengl->texture_name[3]);
                glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, opengl->width, opengl->height, opengl->format, opengl->type,
                                opengl_get_plane_pointer(opengl, pkt, 3, desc));
            }
        }
    }
    ret = AVERROR_EXTERNAL;
    OPENGL_ERROR_CHECK(opengl);

    if ((ret = opengl_prepare(opengl)) < 0)
        goto fail;

    opengl->glprocs.glBindBuffer(FF_GL_ARRAY_BUFFER, opengl->vertex_buffer);
    opengl->glprocs.glBindBuffer(FF_GL_ELEMENT_ARRAY_BUFFER, opengl->index_buffer);
    opengl->glprocs.glVertexAttribPointer(opengl->position_attrib, 3, GL_FLOAT, GL_FALSE, sizeof(OpenGLVertexInfo), 0);
    opengl->glprocs.glEnableVertexAttribArray(opengl->position_attrib);
    opengl->glprocs.glVertexAttribPointer(opengl->texture_coords_attrib, 2, GL_FLOAT, GL_FALSE, sizeof(OpenGLVertexInfo), 12);
    opengl->glprocs.glEnableVertexAttribArray(opengl->texture_coords_attrib);

    glDrawElements(GL_TRIANGLES, FF_ARRAY_ELEMS(g_index), GL_UNSIGNED_SHORT, 0);

    ret = AVERROR_EXTERNAL;
    OPENGL_ERROR_CHECK(opengl);

#if HAVE_SDL
    if (!opengl->no_window)
        SDL_GL_SwapBuffers();
#endif
    if (opengl->no_window &&
        (ret = avdevice_dev_to_app_control_message(h, AV_DEV_TO_APP_DISPLAY_WINDOW_BUFFER, NULL , 0)) < 0) {
        av_log(opengl, AV_LOG_ERROR, "Application failed to display window buffer.\n");
        goto fail;
    }

    return 0;
  fail:
    return ret;
}

static int opengl_write_packet(AVFormatContext *h, AVPacket *pkt)
{
    return opengl_draw(h, pkt, 0);
}

#define OFFSET(x) offsetof(OpenGLContext, x)
#define ENC AV_OPT_FLAG_ENCODING_PARAM
static const AVOption options[] = {
    { "background",   "set background color",   OFFSET(background),   AV_OPT_TYPE_COLOR,  {.str = "black"}, CHAR_MIN, CHAR_MAX, ENC },
    { "no_window",    "disable default window", OFFSET(no_window),    AV_OPT_TYPE_INT,    {.i64 = 0}, INT_MIN, INT_MAX, ENC },
    { "window_title", "set window title",       OFFSET(window_title), AV_OPT_TYPE_STRING, {.str = NULL}, 0, 0, ENC },
    { NULL }
};

static const AVClass opengl_class = {
    .class_name = "opengl outdev",
    .item_name  = av_default_item_name,
    .option     = options,
    .version    = LIBAVUTIL_VERSION_INT,
};

AVOutputFormat ff_opengl_muxer = {
    .name           = "opengl",
    .long_name      = NULL_IF_CONFIG_SMALL("OpenGL output"),
    .priv_data_size = sizeof(OpenGLContext),
    .audio_codec    = AV_CODEC_ID_NONE,
    .video_codec    = AV_CODEC_ID_RAWVIDEO,
    .write_header   = opengl_write_header,
    .write_packet   = opengl_write_packet,
    .write_trailer  = opengl_write_trailer,
    .control_message = opengl_control_message,
    .flags          = AVFMT_NOFILE | AVFMT_VARIABLE_FPS | AVFMT_NOTIMESTAMPS,
    .priv_class     = &opengl_class,
};