[gst-devel] neutral buffer handling in sparse streams

Thu Oct 4 09:49:10 CEST 2007

Hi,

I am fine with defining _GAP as that this is data hat can be ignored.  
It does not break audioresample and once we have a usecase for e.g.  
comfort-noise we could add a _FILLER flag. Regarding the latter I  
wonder whats the benefit for having a such a flag. What kind of  
special handling would an element do when receiving a _FILLER buffer?

Stefan

Quoting Wim Taymans <wim.taymans at gmail.com>:

>
> On Wed, 2007-10-03 at 10:18 -0700, Steve Fink wrote:
>> I'm not sure if I like this suggestion, but it strikes me that by far
>> the most common use case for GST_BUFFER_FLAG_GAP would be when the
>> contents of the buffer really are irrelevant (or neutral, or whatever
>> you want to call it). So perhaps what is needed is an extra flag to
>> say that the buffer contains "gap filler" data in the less common
>> cases.
>
> Sounds like you want to redefine _GAP to mean a buffer that contains no
> relevant data, which is what it currently contains (only audiorate
> produces such buffers AFAIK and they contain silence) but is not clearly
> stated in the docs. I'm perfectly fine with that, provided we make sure
> that other data used to fill a gap (confort noise, frame duplication or
> reconstruction) does not use that flag. If that's fine with everybody,
> we'll do it like that and don't create another flag.
>
> Wim
>
>>
>> On the plus side, this gives more information to the buffer consumer.
>> So, for example, an application-aware mixer might decide to discard
>> gap fillers if any input was non-gap, and keep only one of the gap
>> fillers (rather than mixing all of them) if all inputs were gap
>> fillers. Or whatever.
>>
>> On the minus side, dependent flags are ugly. But making them
>> independent (_GAP and _HAS_DATA_OF_INTEREST, maybe?) means that the
>> other flag would need to default to "on" in the non-gap case, which is
>> no good. Also, using up a flag for a niche case is unfortunate.
>>
>> But I just wanted to throw it out there.
>>
>>
>> On 10/3/07, Wim Taymans <wim.taymans at gmail.com> wrote:
>> >
>> > On Wed, 2007-10-03 at 08:24 +0200, Stefan Kost wrote:
>> > > hi,
>> > >
>> > > Quoting David Schleef <ds at schleef.org>:
>> > >
>> > > > On Mon, Oct 01, 2007 at 10:33:35PM +0300, Stefan Kost wrote:
>> > > >> So what the way to go?
>> > > >>
>> > > >> 1) use GST_BUFFER_FLAG_GAP and define it as such
>> > > >> btw. its right now only used in
>> > > >> gst-plugins-base/gst/audiorate/gstaudiorate.c to
>> > > >> mark a silent filler-buffer
>> > > >>
>> > > >> 2) add GST_BUFFER_FLAG_NEUTRAL
>> > > >>
>> > > >> 3) segments
>> > > >>
>> > > >> 4) anything else?
>> > > >
>> > > > 5) Push subbuffers of a well-known read-only buffer containing only
>> > > > zeros.  (Let's call it gst_buffer_zero.)
>> > > >
>> > > Interesting idea. We could subclass GstBuffer as GstZeroBuffer and
>> > > then elements can check with GST_IS_ZERO_BUFFER.
>> >
>> > Problem is that not all formats of silence have 0 bytes (unsigned audio
>> > for example).
>> >
>> > I still think a good flag that works for audio, video, text, .. is the
>> > way to go. I have problems with a good name, maybe
>> > GST_BUFFER_FLAG_EMPTY, GST_BUFFER_FLAG_VOID, GST_BUFFER_FLAG_ZERO,
>> > GST_BUFFER_FLAG_DEFAULT?
>> >
>> > We don't have much space to add new buffer flags (we can add 3 more):
>> >
>> >   GST_BUFFER_FLAG_DELTA_UNIT = (GST_MINI_OBJECT_FLAG_LAST << 4),
>> >   /* padding */
>> >   GST_BUFFER_FLAG_LAST       = (GST_MINI_OBJECT_FLAG_LAST << 8)
>> >
>> > Another idea is to specify some format specific flags like:
>> >
>> >   ...
>> >   GST_BUFFER_FLAG_CUSTOM1 = (GST_MINI_OBJECT_FLAG_LAST << 5),
>> >   GST_BUFFER_FLAG_CUSTOM2 = (GST_MINI_OBJECT_FLAG_LAST << 6),
>> >   ...
>> >
>> > And then define what they mean for audio/video. We could need something
>> > like this to mark interlaced video frames. One of those custom flags
>> > could be used to mark 'silent' audio buffers.
>> >
>> > Wim
>> >
>> > > >
>> > > > I'm not recommending it, just suggesting it as an alternative  
>>  that we've
>> > > > discussed in the past.  It has the minor advantage of being   
>> transparent
>> > > > to elements that don't know how to handle it.
>> > > >
>> > > >
>> > > >
>> > > > dave...
>> > > >
>> > > >
>> > > >
>> > -------------------------------------------------------------------------
>> > > > This SF.net email is sponsored by: Microsoft
>> > > > Defy all challenges. Microsoft(R) Visual Studio 2005.
>> > > > http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/
>> > > > _______________________________________________
>> > > > gstreamer-devel mailing list
>> > > > gstreamer-devel at lists.sourceforge.net
>> > > > https://lists.sourceforge.net/lists/listinfo/gstreamer-devel
>> > > >
>> > >
>> > >
>> > >
>> > >   
>> -------------------------------------------------------------------------
>> > > This SF.net email is sponsored by: Microsoft
>> > > Defy all challenges. Microsoft(R) Visual Studio 2005.
>> > > http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/
>> > > _______________________________________________
>> > > gstreamer-devel mailing list
>> > > gstreamer-devel at lists.sourceforge.net
>> > > https://lists.sourceforge.net/lists/listinfo/gstreamer-devel
>> >
>> >
>> > -------------------------------------------------------------------------
>> > This SF.net email is sponsored by: Microsoft
>> > Defy all challenges. Microsoft(R) Visual Studio 2005.
>> > http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/
>> > _______________________________________________
>> > gstreamer-devel mailing list
>> > gstreamer-devel at lists.sourceforge.net
>> > https://lists.sourceforge.net/lists/listinfo/gstreamer-devel
>> >
>
>
> -------------------------------------------------------------------------
> This SF.net email is sponsored by: Splunk Inc.
> Still grepping through log files to find problems?  Stop.
> Now Search log events and configuration files using AJAX and a browser.
> Download your FREE copy of Splunk now >> http://get.splunk.com/
> _______________________________________________
> gstreamer-devel mailing list
> gstreamer-devel at lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/gstreamer-devel
>