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<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Thanks.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>If decoding from the last packet on the previous page works,
I may have to do that. But I was hoping to avoid it. Yes, I may be seeking a
lot. A packet spanning multiple pages shouldn't be a problem for me, because
I'm only adding index points that represent the beginning of a packet. But does
this actually happen for Vorbis? (Aside from large header packets) The large
blocks I've encountered seem to be 1024 samples per channel. Even with
8-channel audio, uncompressed floating-point PCM sound, such a packet would
only take up 129 segments on the segment table.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><st1:City w:st="on"><st1:place w:st="on"><font size=2
face=Arial><span style='font-size:10.0pt;font-family:Arial'>Madison</span></font></st1:place></st1:City><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>From: Jordan Verner [mailto:jv_erner@hotmail.com] <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Sent: Tuesday, May 19, 2015 12:20 PM<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>To: Madison Link<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Subject: RE: [Vorbis] How do I seek to seek to specific
samples using libvorbis?<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>What I did was performed a binary search in my ogg vorbis
file, in order to find the page proceeding the page containing the desired
sample (you can determine this using the granule position). Next, I used
ogg_page_packets() to determine how many packets complete on that page, skip to
the final packet by calling ogg_stream_packetout N times and just ignoring the
result. Then decode the page's final packet. This should mean that the next
sample you decode will actually be the one the granule position says it is.
Then you have to calculate an offset between the sample you're at and the one
you want, decode that many and discard them. In practice this seems to work but
leaves a lot to be desired. You could be decoding up to an entire page of audio
(slow if you seek a lot), and there's an off chance that a complex and rare
case involving a packet spanning three or more pages could still throw you off.
I think it could be possible to do it with only decoding two extra packets if
you can calculate where you'll end up based on blocksize values and window
overlapping rules, but it's not well explained. The spec leaves a lot to be
desired.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> <o:p></o:p></span></font></p>
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