[Swftools-common] audio sync and mp3 compression

[Pablo Rodríguez]

Hi there,

after some experiments the devel version trying to sync a pdf
presentation and a mp3 file, I discovered some issues with the following
script:

# jono-bacon.sc
.flash filename="jono-bacon+.swf" fps=1
    .swf slides "jono-bacon.swf"
    .put slides
    .stop slides
    .sound audio filename="jono-bacon.wav.mp3"
    .play audio

    .frame n+=10 #slide1 00:10
        .nextframe slides
    .frame n+=10 #slide2 00:20
        .nextframe slides
    .frame n+=10 #slide3 00:30
        .nextframe slides
    .frame n+=10 #slide4 00:40
        .nextframe slides
    .frame n+=10 #slide5 00:50
        .nextframe slides
    .frame n+=2 #slide6 00:52
.end

Audio is played at right speed only if it is => 32 kbps (with 'lame -m m
-b 32 --cbr audio.mp3). If I use 16 kbps, audio is played slower than it
should be and if I use 800 bps, audio is played faster than it should
be. (I wonder whether lame doesn't apply CBR bellow 32 kbps or swfc has
problems to recognize it.)

Using wav2swf -b 16, audio is played fine in output.swf, but using -b 8
nothing is played (or there is nothing to listen to). I got the wav file
generated from Audacity 1.2.4.

By the way, how can I sync audio and a presentation so that audio is
fully synced with slides? I mean, the SWF file contains a previewer and
the next slide is selected, the audio begins to play at next slide and
doesn't go playing where it was, as it happens now. (I guess the
solution would be the proper switches in swfcombine.)

Thanks,


Pablo