Now I got a different way to pinpoint this.

I looked at the original sound used in making of gears.swf, it virtually has no silence period.
But sound extracted from gears.swf, I found out that it has ~100 ms slience gap at the beginning and ending.

When I compare this extracted sound side-by-side with ones recorded during gnash (0.8.10) playing gears.swf;
it matched, thus gnash is playing a raw sound data (which includes spaces).

So I manually applied SeekSamples and SoundSampleCount on the extracted sound data.
I found that this precisely clips the gap out both on the start and at the end.
This clipped sound played continuously, like Macromedia Flash Player do.


Summed up: I think SeekSamples+SoundSampleCount functionality were needed to play the sound correctly.




Note #1: The attached file (gears-sounds.zip) contains
peak-graph of sounds and comparision in my experiment (sounds.png),
the original sound (gears-original.wav),
extracted sound (gears-extracted.wav),
looped version of extracted sound (gears-extracted.loop.wav),
clipped (applied SeekSamples+SoundSampleCount) version of extracted sound (gears-clipped.wav),
clipped and looped version of extracted sound (gears-clipped.loop.wav) aka. the final result.

Note #2: These experiments were done under sound editor, which allowed me to do them only down to millisecond precision, enough to demonstrate what these parameters do, but it's not sample-by-sample accurate.

(file #25257)

I just checked gears.swf's sound embedding in source fla file, it wasn't a "Sync: Stream", but a "Sync: Start".
Sorry for my mistake on the first post.

Sorry, 5182 is 1/32 and gives you the gap, while 10364 doesn't give you the gap.

The problem seems to be with the start of decoding data:
decodedDataSize: 165824

Setting _inPoint to 1/16 of that makes the sound come out smooth.

Note that gnash doesnt' support the "Mp3: SeekSamples 1670" part, so if the mp3 starts with 1670 silent samples we could have an explanation for this. Haven't checked more closely yet.

This may also be a duplicate of bug #24481

Hello, I'm using gnash 0.8.9-1~lenny from getgnash.org apt repository.
When playing my dummy flash file created from Flash MX 2004 (Flash 7)
background sound that's supposed to repeat continuously,
just plays for 1 sec, stops and restarted, and things repeated again.
Animation plays fine, though.

http://www.mediafire.com/?3a3lxxl7iek3w90
This is a 'correct' result from Macromedia Flash Player 7
(You will notice that sound play all along the animation)

http://www.mediafire.com/?fzzbj9ttt7nz3s8
This is a video result from Gnash
(You will notice that sound play,stop,play,stop,... all along)

http://www.mediafire.com/?qq1r0vkic3y3e3b
This is my dummy flash file (created from Flash MX 2004), also attached here.


System: Debian GNU/Linux 5.0 Lenny on i386

Note: Sound was embedded in timeline as 'stream'