Clever Geek Handbook

Bagaimana mengembangkan analog Zoom untuk TV box di RDK dan Linux. Memahami kerangka GStreamer

Skenario: Cara Menggunakan Aplikasi Konferensi Video di SmartTV dan Set-Top Boxes
Skenario: Cara Menggunakan Aplikasi Konferensi Video di SmartTV dan Set-Top Boxes

Pandemi COVID-19 telah menjadi katalisator untuk layanan baru yang bermanfaat. Misalnya, Zoom telah menjadi begitu sukses sehingga melampaui nilai IBM bulan ini. Kami terinspirasi oleh contoh ini, dan kami memutuskan untuk melangkah lebih jauh: bagaimana jika konferensi online diterapkan di dekoder dan Smart TV untuk berkomunikasi tidak hanya di tempat kerja, tetapi untuk mengatur pertemuan jarak jauh di sofa dengan teman-teman? Tapi kemudian Anda bisa berteriak bersama di sepak bola, menonton film atau berolahraga di bawah pengawasan seorang pelatih. 

- , - Linux/Android RDK. « Zoom» Smart TV. GStreamer. , .

- . , desktop-, , , embedded- .

, -:

  1. . STB-   ARM-, , / . , — .

  2. . Android, — RDK, — Linux . . desktop-. .

  3. . Ethernet wifi. / — .

  4. . .

  5. .

. Zoom - :

  • /

  • /

:

Arsitektur aplikasi konferensi video Smart TV
Smart TV

GStreamer, .. .

/  

1) GStreamer

, . , 30 640x480. , RGB24 :

640 480 3 30 = 27 648 000 , .. 26 , .

— - . , , GStreamer. ? :

  1. Linux Android.

  2. RDK Gstreamer / -.

  3. , . FFmpeg, , - GStreamer’.

  4. (pipeline). / , , .

  5. API /C++ .

  6. /, OpenMAX API — -.

2) GStreamer  

, , .  GStreamer , :

gst-inspect-1.0 , , , .

gst-launch-1.0 (pipeline).

GStreamer , , source, sink-. source — , ,  (sink) — , , ( RTP).

. mp4-:

gst-launch-1.0 filesrc location=file.mp4 ! qtdemux ! h264parse ! avdec_h264 ! videoconvert ! autovideosink

mp4-, mp4 — qtdemux, h264, , , , .

autovideosink filesink .

3) GStreamer C/C++ API.

, gst-launch-1.0, , . : (pipeline), GStreamer glib-.

filesrc filesink — «GStreamer: ». H264-.

GStreamer-

gstinit (NULL, NULL);

, 

gst_debug_set_active(TRUE);
gst_debug_set_default_threshold(GST_LEVEL_LOG);

: , gstinit .

event-loop, :

GMainLoop *loop;
loop = g_main_loop_new (NULL, FALSE);

:

, GstElement:

GstElement *pipeline, *source, *demuxer, *parser, *decoder, *conv, *sink;

pipeline = gst_pipeline_new ("video-decoder");
source   = gst_element_factory_make ("filesrc",       "file-source");
demuxer  = gst_element_factory_make ("qtdemux",      "h264-demuxer");
parser   = gst_element_factory_make ("h264parse",      "h264-parser");
decoder  = gst_element_factory_make ("avdec_h264",     "h264-decoder");
conv     = gst_element_factory_make ("videoconvert",  "converter");
sink     = gst_element_factory_make ("appsink", "video-output");

gst_element_factory_make, , — GStreamer, , , .

, , gst_element_factory_make NULL.

if (!pipeline || !source || !demuxer || !parser || !decoder || !conv || !sink) {
		//     - 
		return;
}

location gob_ject_set:

gob_ject_set (G_OBJECT (source), "location", argv[1], NULL);

.

GStreamer, bus_call:

GstBus *bus;
	guint bus_watch_id;
	bus = gst_pipeline_get_bus (GST_PIPELINE (pipeline));
	bus_watch_id = gst_bus_add_watch (bus, bus_call, loop);
	gst_object_unref (bus);

gst_object_unref .

:

static gboolean
bus_call (GstBus     *bus,
          GstMessage *msg,
          gpointer    data)
{
  GMainLoop *loop = (GMainLoop *) data;

  switch (GST_MESSAGE_TYPE (msg)) {

    case GST_MESSAGE_EOS:
      LOGI ("End of stream\n");
      g_main_loop_quit (loop);
      break;

    case GST_MESSAGE_ERROR: {
      gchar  *debug;
      GError *error;

      gst_message_parse_error (msg, &error, &debug);
      g_free (debug);

      LOGE ("Error: %s\n", error->message);
      g_error_free (error);

      g_main_loop_quit (loop);
      break;
    }
    default:
      break;
  }

  return TRUE;
}

: , gst-launch. , , :

gst_bin_add_many (GST_BIN (pipeline), source, demuxer, parser, decoder, conv, sink, NULL);
gst_element_link_many (source, demuxer, parser, decoder, conv, sink, NULL);

, , (autovideosink) :

  gst_element_link (source, demuxer);
  gst_element_link_many (parser, decoder, conv, sink, NULL);
  g_signal_connect (demuxer, "pad-added", G_CALLBACK (on_pad_added), parser);

static void
on_pad_added (GstElement *element,
              GstPad     *pad,
              gpointer    data)
{
  GstPad *sinkpad;
  GstElement *decoder = (GstElement *) data;

  /* We can now link this pad with the sink pad */
  g_print ("Dynamic pad created, linking demuxer/decoder\n");

  sinkpad = gst_element_get_static_pad (decoder, "sink");

  gst_pad_link (pad, sinkpad);

  gst_object_unref (sinkpad);
}

, .

, , :

gst_element_set_state (pipeline, GST_STATE_PLAYING);

event-loop:

g_main_loop_run (loop);

:

gst_element_set_state (pipeline, GST_STATE_NULL);
  gst_object_unref (GST_OBJECT (pipeline));
  g_source_remove (bus_watch_id);
  g_main_loop_unref (loop);

4) .

, — , .

gst_element_factory_find, , factory :

if(gst_element_factory_find("omxh264dec"))
		decoder  = gst_element_factory_make ("omxh264dec",     "h264-decoder");
	else
		decoder  = gst_element_factory_make ("avdec_h264",     "h264-decoder");

OMX RDK, .

, , GstElement ( ):

gst_plugin_feature_get_name(gst_element_get_factory(encoder))

.

5)

, . YUV, RGB.

YUYV. , GStreamer, I420. , gl-, I420-. . , .

GStreamer’ , , - . 

 

1)

  . , , filesrc filesink .

appsrc / appsink. - . 

, ? , . , I420. , ? ?

need-data, :

g_signal_connect (source, "need-data", G_CALLBACK (encoder_cb_need_data), NULL);

:

encoder_cb_need_data (GstElement *appsrc,
          guint       unused_size,
          gpointer    user_data)
{
  GstBuffer *buffer;
  GstFlowReturn ret;
  GstMapInfo map;

   int size;
   uint8_t* image;
  // get image

  buffer = gst_buffer_new_allocate (NULL, size, NULL);
  gst_buffer_map (buffer, &map, GST_MAP_WRITE);
  
  memcpy((guchar *)map.data, image,  gst_buffer_get_size( buffer ) );
  gst_buffer_unmap(buffer, &map);

  g_signal_emit_by_name (appsrc, "push-buffer", buffer, &ret);
  gst_buffer_unref(buffer);
}

image — , , I420.

gst_buffer_new_allocate , .

gst_buffer_map , memcpy, . 

, , GStream’ , .

: gst_buffer_unmap, gst_buffer_unref. . , , , .

, , : caps .

need-data:

	g_object_set (G_OBJECT (source),
        "stream-type", 0,
        "format", GST_FORMAT_TIME, NULL);

	g_object_set (G_OBJECT (source), "caps",
		gst_caps_new_simple ("video/x-raw",
					"format", G_TYPE_STRING, "I420",
					"width", G_TYPE_INT, 640,
					"height", G_TYPE_INT, 480,
					"framerate", GST_TYPE_FRACTION, 30, 1,
		NULL), 
	NULL);

GstElement, g_object_set.

, caps — . , appsrc I420 c 640x480 30 .

, , . , GStreamer - need-data .

, . 

2)

, .

sink pad:

	GstPad *pad = gst_element_get_static_pad (sink, "sink");
  	gst_pad_add_probe  (pad, GST_PAD_PROBE_TYPE_BUFFER, encoder_cb_have_data, NULL, NULL);
  	gst_object_unref (pad);

sink pad — GST_PAD_PROBE_TYPE_BUFFER, — sink pad.

static GstPadProbeReturn
encoder_cb_have_data (GstPad * pad,
                        GstPadProbeInfo * info,
                        gpointer user_data) {

  GstBuffer *buf = gst_pad_probe_info_get_buffer (info);
  GstMemory *bufMem = gst_buffer_get_memory(buf, 0);
  GstMapInfo bufInfo;
  gst_memory_map(bufMem, &bufInfo, GST_MAP_READ);

  // bufInfo.data, bufInfo.size

  gst_memory_unmap(bufMem, &bufInfo);

  return GST_PAD_PROBE_OK;
}

. . GstBuffer, , gst_buffer_get_memory 0 ( ). , , gst_memory_map, bufInfo.data bufInfo.size.

— .

, Smart TV — Zoom -: , / GStreamer, / .

. — — embedded- RDK, Linux Android. — , .

Ide dengan layanan konferensi video melalui Smart TV ini dapat dikembangkan lebih lanjut, baik dari segi solusi teknik maupun skenario penggunaannya. Jadi bagikan pemikiran Anda di komentar. 



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