<br>
4) Subtract 1 from the keyframe, then repeat step 3).<br>
<br>
5) Begin reading from the frame discovered in step 4. Drop any packets<br>
which are output on the first page. Count down until we reach the<br>
keyframe, dropping packets until then.<br>
<br>
6) Continue counting down until we reach the target frame, we are now<br>
decoding each frame/packet. At the target frame produce the YUV<br>
output.<br><br>Steps 4 and 5 are necessary because ogg only tells
you where a frame ends, not where it
starts.<br><br><br><br>My code has two further
optimisations:<br>- if playing sequentially (current_frame - last_frame
< threshold), you don't need to seek again (from trial and error
I found threshold is best if it is around 1/4 of the keyframe_granule_shift).
Just continue decoding.<br>
<br>- I create a hash table of largest granule pos -> keyframe as
this is discovered. Doing a binary tree search of this first can help narrow the
initial search range for keyframes which have already been discovered<br>
<br>It's all in the code here:<br><a
href=3D"http://lives.svn.sourceforge.net/viewvc/lives/trunk/lives-plugins/plugins/decoders/ogg_theora_decoder.c">http://lives.svn.sourceforge.net/viewvc/lives/trunk/lives-plugins/plugins/decoders/ogg_theora_decoder.c</a><br>
<br>The only function to really consider is get_frame() which takes a
(const) char *URI (actually the current version really only takes a local file
name), and an int64_t frame number and returns the output in void *pixel_data[3]
which should be pre-allocated to take a correctly sized YUV420 frame. The rest
is just internal functions or decoration, apart from get_clip_data() which
returns a struct with all the details about (const) char *URI. I only
implemented video (theora) decoding, but it should be fairly easy to implement
audio decoding from the same pages.<br>
<br>Yes, it is a bit complicated, but it really is the only way if you
want 100% accurate seeking in an ogg
container.<br><br><br><br>Salsaman.<br><br
clear=3D"all"><br><a
href=3D"http://lives.sourceforge.net">http://lives.sourceforge.net</a><br>
<a
href=3D"https://www.ohloh.net/accounts/salsaman">https://www.ohloh.net/accounts/salsaman</a><br><br>
<br><br><div class=3D"gmail_quote">On Mon, Mar 15,
2010 at 4:22 PM, Nigel Simpson <span dir=3D"ltr"><<a
href=3D"mailto:nigel at
matsuplace.com">nigel@matsuplace.com</a>></span>
wrote:<br><blockquote class=3D"gmail_quote"
style=3D"border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt
0.8ex; padding-left: 1ex;">
<div bgcolor=3D"#FFFFFF"><div>I know of a bunch of
developers and students who might be available to help out. I figure this issue
needs Cortado experts rather than lots of developers, though. If that's
not the case and you need some help, I can send some people to the
project.</div>
<div><br></div><font
color=3D"#888888"><div>Nigel=A0</div></font><div><div></div><div
class=3D"h5"><div><br></div><div>On Mar 15,
2010, at 12:08 PM, "<a href=3D"mailto:ozemale at
ozemail.com.au" target=3D"_blank">ozemale at
ozemail.com.au</a>" <<a href=3D"mailto:ozemale at
ozemail.com.au" target=3D"_blank">ozemale at
ozemail.com.au</a>> wrote:<br>
<br></div><div></div><blockquote
type=3D"cite"><div><br>
I also have a pressing need to have the seeking/pausing issues in Cortado
resolved.<br>
<br>
What do we need to do to get these issues addressed and resolved?<br>
<br>
Thanks,<br>
<br>
John<br>
<br>
<span style=3D"font-weight: bold;">On Mon Mar 15 11:54 , Nigel
Simpson sent:<br>
<br>
</span><blockquote style=3D"border-left: 2px solid rgb(245, 245,
245); margin-left: 5px; margin-right: 0px; padding-left: 5px; padding-right:
0px;">On Mar 15, 2010, at 3:59 AM, "<a></a><a
href=3D"mailto:ogg.k.ogg.k at googlemail.com"
target=3D"_blank">ogg.k.ogg.k at googlemail.com</a>"
<<a></a><a href=3D"mailto:ogg.k.ogg.k at
googlemail.com" target=3D"_blank">ogg.k.ogg.k at
googlemail.com</a> <br>
> wrote:<br>
<br>
>> When I play the converted video using cortado 0.5.2, seeking
still <br>
>> seems to<br>
>> be broken. For example: play a video, pause and then press
play, <br>
>> the player<br>
>> resumes several seconds after the paused position. Also, pause
and <br>
>> drag the<br>
>> time slider. The slider jumps to a new position after you
release <br>
>> the drag<br>
>> rather than where the slider was dragged.<br>
>><br>
>> Does cortado support OggIndex?<br>
><br>
> No. The index is a very new addition and is still being worked
on.<br>
> Support at the moment is limited to ffmpeg2theora and OggIndex
(plus<br>
> patches for Firefox). It is expected that various players will
be<br>
> patched to support the index, however. Cortado would probably be
one<br>
> of them.<br>
<br>
That would be great to see in Cortado.<br>
<br>
>> Are there any workarounds for reliably getting and setting the
<br>
>> playback<br>
>> position?<br>
><br>
> Seeking is known to have problems in Cortado. They're fixed as
<br>
> they're found.<br>
> Also, a recently released version of Cortado had a
non-working<br>
> playback position access from Javascript, in case you're also
seeing<br>
> this problem. I'm unsure whether there was a release since this
was<br>
> found.<br>
<br>
I'm using Cortado in a Java application, and have been trying to
<br>
figure out why Cortado can seek reliably (well, reproducibly perhaps)
<br>
but doesn't reliably report the current position, or resume from pause
<br>
properly. It sounds like these are known issues though. Is there any <br>
way to raise the priority of these issues?<br>
<br>
Nigel<br>
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</blockquote>
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