Re: [libav-devel] [PATCH] ffplay: notify user about audio metadata switch

2011-04-29 Thread Ronald S. Bultje
Hi,

On Fri, Apr 29, 2011 at 12:45 PM, Clément Bœsch ubi...@gmail.com wrote:
 On Fri, Apr 29, 2011 at 07:27:26AM +0200, Vladimir Pantelic wrote:
 On 04/28/2011 05:10 PM, Ronald S. Bultje wrote:
 Hi,
 
 On Thu, Apr 28, 2011 at 3:05 PM, Clément Bœschubi...@gmail.com  wrote:
 This patch allows users to be notified about track switch on a continuous
 audio stream. The A-V statusbar mess up a bit the printing sometimes, I
 don't know how I should handle that. Also, I wonder if there is an
 performance issue looping on every metadata that often.
 
 Seems like a case where introducing a metadata_changed message
 somewhere would help. Maybe in AVPacket.side_data? :-).

 This is not really simple to handle when you are in the metadata scope:
 metadata functions don't have access the AVPacket, it would require a few
 changes.


 since metadata can change out-of-band, what pkt would you attach it to?

 why not make a simple counter in metadata that increases on each change,
 then users don't have to md5sum it to know if it was modified?

 I tried that, but it would require an API modification, and actually it
 does not work for a simple reason: the metadata allocation is completely
 destroyed and a new one is created on track switch. So you might have the
 same amount of update count (which is actually the same value as the
 count field) while it's total different values.

 But, the good news is that since it's a different pointer, we can just
 based the code on this. Of course, this is assuming all other continuous
 streams demuxers won't add new fields and purges the old ones, but it
 looks improbable because of the complexity.

 New simpler patch attached.

Not that I'm completely against this patch, after all it's only
metadata (don't take that badly Anton), but the update wouldn't
reflect when it took effect. I think that is what side_data is for. In
fact, I believe metatadata should be moved entirely into side-data
when it updates midstream, just like palettes.

Ronald
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Re: [libav-devel] [PATCH] ffplay: notify user about audio metadata switch

2011-04-28 Thread Kostya
On Thu, Apr 28, 2011 at 03:10:03PM +, Ronald S. Bultje wrote:
 Hi,
 
 On Thu, Apr 28, 2011 at 3:05 PM, Clément Bœsch ubi...@gmail.com wrote:
  This patch allows users to be notified about track switch on a continuous
  audio stream. The A-V statusbar mess up a bit the printing sometimes, I
  don't know how I should handle that. Also, I wonder if there is an
  performance issue looping on every metadata that often.
 
 Seems like a case where introducing a metadata_changed message
 somewhere would help. Maybe in AVPacket.side_data? :-).

it will be present only in undecoded freshly demuxed packet. If that's fine
for you feel free to use side data there.
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