Video quality lost when converting from .ogg to .mp4

[Trever Fischer]

On Monday, June 06, 2011 10:46:55 AM William Metcalf wrote:
> Hello all,
> 
> I have written a gstreamer C application to convert a .ogg to .mp4
> file.  The application is successful at converting the video and audio,
> but the video produced after the conversion is of much lower quality
> than the original video ( the audio converts with basically no loss I
> can see).  I figure that some loss in video is to be expected, but I was
> wondering what gstreamer modules might be good for helping lower the
> loss in video quality.  Below is a snippet of my code that shows the
> pipeline I used to convert the file.
Converting from a lossy format to a lossy format almost always causes a 
reduction in quality. No real way to avoid that.
> 
> Thank you in advance for your help.
> 
> int main (int argc, char *argv[])
> {
>      gst_init(&argc, &argv);
> 
>      AV = 0;
> 
>      loop = g_main_loop_new(NULL, FALSE);
> 
>      /* Create elements */
>      pipeline            = gst_pipeline_new("audio-player");
> 
>      /* Element for reading in a file */
>      source                = gst_element_factory_make("filesrc",
> "file-source");
> 
>      /* OGG elements */
>      oggdemuxer            = gst_element_factory_make("oggdemux",
> "ogg-demuxer");
>      vorbis_decoder        = gst_element_factory_make("vorbisdec",
> "vorbis-decoder");
>      theora_decoder        = gst_element_factory_make("theoradec",
> "theora-decoder");
> 
>      /* MP4 elements */
>      audio_encoder        = gst_element_factory_make("faac",
> "aac-encoder"); video_encoder        =
> gst_element_factory_make("ffenc_mpeg4", "avc-encoder");
>      mp4_muxer            = gst_element_factory_make("qtmux", "mp4-muxer");
> 
>      /* Audio/Video elements */
>      video_converter        =
> gst_element_factory_make("ffmpegcolorspace", "video-converter");
>      videosink            = gst_element_factory_make("autovideosink",
> "video-sink");
>      video_scale            = gst_element_factory_make("videoscale",
> "video-scale");
>      video_rate            = gst_element_factory_make("videorate",
> "video-rate");
>      audio_resample        = gst_element_factory_make("audioresample",
> "audio-resample");
>      audio_rate            = gst_element_factory_make("audiorate",
> "audio-rate");
>      audiosink            = gst_element_factory_make("autoaudiosink",
> "audio-sink");
>      audio_converter        = gst_element_factory_make("audioconvert",
> "audio-converter");
> 
>      /* Queues */
>      video_queue            = gst_element_factory_make("queue",
> "video-queue");
>      audio_queue            = gst_element_factory_make("queue",
> "audio-queue");
>      video_out_queue        = gst_element_factory_make("queue",
> "video-out-queue");
>      audio_out_queue        = gst_element_factory_make("queue",
> "audio-out-queue");
> 
>      /* Element to write to the file */
>      filesink                = gst_element_factory_make("filesink",
> "file-sink");
> 
>      /* Make sure we were able to create all of the elements*/
>      if(!pipeline || !source || !oggdemuxer || !vorbis_decoder ||
> !theora_decoder || !audio_encoder || !video_encoder || !mp4_muxer ||
> !audio_converter || !video_converter || !audio_resample || !audio_rate
> 
> || !videosink || !audiosink || !video_queue || !audio_queue ||
> 
> !video_out_queue || !audio_out_queue || !video_scale || !video_rate ||
> !filesink )
>      {
>          g_printerr("One ore more elements could not be created.
> Exiting.\n");
>          return -1;
>      }
> 
>      /* Input file */
>      g_object_set(G_OBJECT(source), "location", "c:\\video(1080p).ogg",
> NULL);
>      g_object_set(G_OBJECT(filesink), "location",
> "c:\\Encoder_Output\\video(encoded from ogg).mp4", NULL);
> 
>      /* Add a message handler from pipeline bus */
>      bus = gst_pipeline_get_bus(GST_PIPELINE(pipeline));
>      gst_bus_add_watch(bus, bus_call, loop);
>      gst_object_unref(bus);
> 
>      /* add elements to the pipeline */
>      gst_bin_add_many(GST_BIN(pipeline), source, oggdemuxer,
> video_queue, theora_decoder, video_converter, video_scale, video_rate,
> video_encoder, video_out_queue, audio_queue, vorbis_decoder,
> audio_converter, audio_resample, audio_rate, audio_encoder,
> audio_out_queue, mp4_muxer, filesink, NULL);
> 
>      /* link the elements together */
>      res = gst_element_link(source, oggdemuxer);
>      if(!res)
>      {
>          g_printerr("There was a problem linking filesrc to oggdemux.\n");
>          return 1;
>      }
> 
>      /* video_queue -> theoradec -> ffmpegcolorspace -> ffenc_mpeg4 ->
> video_out_queue ~> qtmux */
>      res = gst_element_link_many(video_queue, theora_decoder,
> video_converter, video_scale, video_rate, video_encoder,
> video_out_queue, NULL);
>      if(!res)
>      {
>          g_printerr("There was a problem linking video elements.\n");
>          return 1;
>      }
>      //link_video_caps(video_scale, video_encoder, 854, 480, 25, 1);
> 
>      /* queue_audio -> vorbisdec -> audioconvert -> faac ->
> audio_out_queue ~> qtmux */
>      res = gst_element_link_many(audio_queue, vorbis_decoder,
> audio_converter, audio_resample, audio_rate, audio_encoder,
> audio_out_queue, NULL);
>      if(!res)
>      {
>          g_printerr("There was a problem linking the audio elements.\n");
>          return 1;
>      }
>      g_signal_connect(oggdemuxer, "pad-added", G_CALLBACK(on_pad_added),
> NULL);
> 
>      /* qtmux -> filesink */
>      res = gst_element_link(mp4_muxer, filesink);
>      if(!res)
>      {
>          g_printerr("There was a problem linking qtmux to filesink.\n");
>          return 1;
>      }
> 
>      link_video_to_multiplexer(video_out_queue, mp4_muxer);
>      link_audio_to_multiplexer(audio_out_queue, mp4_muxer);
> 
> 
>      /* Set the pipeline stat to play and start the main loop*/
>      g_print("Starting the pipeline\n");
>      gst_element_set_state(pipeline, GST_STATE_PLAYING);
>      g_main_loop_run(loop);
> 
>      /* We are done now, do a little bit of cleaning up */
>      g_print("Stopping the pipeline.\n");
>      gst_element_set_state(pipeline, GST_STATE_NULL);
>      gst_object_unref(GST_OBJECT(pipeline));
> 
>      return 0;
> }
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