[gstreamer-bugs] [Bug 494528] New: Simplifications of the LAME plugin

[GStreamer (bugzilla.gnome.org)]

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  GStreamer | gst-plugins-ugly | Ver: HEAD CVS
           Summary: Simplifications of the LAME plugin
           Product: GStreamer
           Version: HEAD CVS
          Platform: Other
        OS/Version: All
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: Normal
         Component: gst-plugins-ugly
        AssignedTo: gstreamer-bugs at lists.sourceforge.net
        ReportedBy: bouvigne at mp3-tech.org
         QAContact: gstreamer-bugs at lists.sourceforge.net
     GNOME version: Unspecified
   GNOME milestone: Unspecified


Current Lame plugin is offering many many options, including some deprecated
ones and potentially harmful ones. I think this is mainly our (Lame devs)
fault, as Lame provides many options to the user that should never had been
provided outside of debug builds.

Since a few years, we are trying to simplify things a lot, and are encouraging
third-party devs to provide a simple user interface instead of the "usual"
options-cluttered one (http://lame.sourceforge.net/lame_ui_example.php).

I think that it might be a good thing to simplify the current Gstreamer Lame
plugin, so I am going to provide a list of comments there. Please tell me if
this should be split into several entries.

#outdated options, not doing anything:
lowpass_width/highpass_width/cwlimit
Those are deprecated, and are just preserved within current Lame API in order
to not break external apps that might still be using them.

#not doing anything usefull:
gboolean extension (ARG_EXTENSION)
This one is just switching a bit within the bistream, for which we never found
any use.

#not needed anymore:
preset(ARG_PRESET)
Not needed since Lame 3.94 (released in 2003). "Presets" are now always
automatically used.

strict_iso(ARG_STRICT_ISO)
Always used

#potentially (mostly always) harmfull for quality, I think they should not be
offered to the user:
force_ms
disable_reservoir
ath_only
ath_short
no_ath
ath_type
ath_lower
allow_diff_short
no_short_blocks

#potential problems:

*Sink pad is audio/x-raw-int. Why not using audio/x-raw-float as the Vorbis
encoder?

*GST_TYPE_LAME_MODE
"auto" is deprecated (better not provide it), "Stereo" should not be used
(joint should be preferred), "Dual Channel" would probably be better understood
if it was named "Dual Content / Dual Channel".

*GST_TYPE_LAME_QUALITY
Default Lame value is 2 (and not 5) since several years ago. I agree that this
one is a bit tricky for you, as current Lame API doesn't really tell you about
the default value.

*DEFAULT_MIN_VBR_BITRATE
Our default is 32 for mpeg1 and 8 for mpeg2. Gstreamer plugin default value is
112, which is way too high.

*DEFAULT_MAX_VBR_BITRATE
Our default is 320 for mpeg1 and 160 for mpeg2. Current plugin value of 160 is
way too low when using mpeg1. I understand that it's probably this way because
this value works both in mpeg1 and mpeg2 case, so solving this would be tricky.

*on GST_EVENT_FLUSH_STOP, you are using a buffer of 7200. Why not always using
the same buffer value, both when encoding and on closing? (mp3_buffer_size =
1.25 * num_samples + 7200)
7200 will sometimes not be big enough.


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