[theora-dev] encoder discrepancy

Mauricio Piacentini mauricio at tabuleiro.com
Mon Jun 2 12:23:52 PDT 2003

Hi, guys. I have verified output on Windows and Linux builds using the new
encoder sample, and also added a new example that will make this task easier
to do in the future. The example is dump_video, it is checked in the tree
with a unix makefile and a companion win32 project.

What this sample does is to decompress only the Theora frames and output the
YUV to a file, ignoring ogg pages and structures and other streams (like
vorbis.) Comparing the binary output should produce identical results on a
given platform. With this tool I can see that the YUV output is the same for
files compressed on Windows and on Linux.

Just fyi: the binary ogg files generated on Linux and Windows are different.
If you encode without audio (only theora) the differences will be only the
streamids and CRC bytes. But if you add vorbis data then the output will be
very different. However, this does not appear to be a Theora issue or an
issue with our encoders. If you use oggenc and encode the exact same wave
file on Win and Linux you will get different binary outputs, not only in the
stream headers but in the actual data as well. Apparently this is caused by
rounding differences, at least this is what was hinted to me in IRC.

Mauricio Piacentini

<p>----- Original Message ----- 
From: "Dan Miller" <dan at on2.com>
To: <theora-dev at xiph.org>
Sent: Thursday, May 29, 2003 12:40 AM
Subject: [theora-dev] encoder discrepancy

<p>> the files produced by windows compile vs. Linux are indeed significantly
different in size (about 140K vs. 160)  However I'm not convinced all the
default parameters are set the same way in the two example files.  This
needs to be verified to see if there really is a bug, or can the two
versions produce byte-equal output streams?

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