[gstreamer-bugs] [Bug 572973] buffer size request event

[GStreamer (bugzilla.gnome.org)]

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  GStreamer | gstreamer (core) | Ver: git




------- Comment #2 from Stefan Kost (gstreamer, gtkdoc dev)  2009-02-26 08:40 UTC -------
encoders would want to request a number of samples:
- mp3: a frame that consists of 384, 576, or 1152 samples
 (depends on MPEG version and layer)
- aac: a frame always consists of 1024 samples

dunno if ther eare difference in mono/stereo. problem is that sources work in
bytes (at least if we implement it in basesrc via blocksize). It means the
request needs to be converted when passing it along. there could be even the
case of:
8bitaudiosrc ! audioconvert ! audioenc

if audioenc request 1024 samples a 16bit = 2048 bit from audioconvert, then
audioconvert will request 1024 samples a 8bit from 8bitaudiosrc.

Regarding comment #1. I need to figure when extactly a buffer-size-request
should be sent. In the _chain function the encoder could do:

gst_xxx_chain(GstElement *self,GstBuffer *buf)
{
  GstBuffer *in;

  if((G_LIKELY(gst_adapter_available(self->adapter)==0) &&
(GST_BUFFER_SIZE(buf)==wanted_size)) {
    in=buf;
  } else {
    gst_adapter_push(self->adapter,buf);
    in=gst_adapter_take_buffer(self->adapter,wanted_size);
    if(in==NULL) ... /* need more */
  }

  ...

  gst_buffer_unref(in);
}

It mean the adapter would only be used if we ever get a frame that is no the
wanted size.


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