[theora-dev] Theora file size

David Kuehling dvdkhlng at gmx.de
Fri Oct 6 08:04:51 PDT 2006

>>>>> "Unga" == Unga  <unga888 at yahoo.com> writes:

> Hi I was surprised with size of Theora files and thought of feedback.

> Following 1minute duration Theora and Xvid files were made from a y4m
> file. The resolution is 1280x720:

> 1. Xvid 17MB 2. Ogg/Theora Q7 31MB 3. Ogg/Theora Q8 38MB 4. Ogg/Theora
> Q9 49MB 5. Ogg/Theora Q10 61MB

> The Xvid file was made using mencoder by 2 passes with following
> options:
> bitrate=2500:autoaspect:chroma_opt:vhq=4:bvhq=1:quant_type=mpeg:pass=1

> The encoder_example was used to create Ogg/Theora files.


two things come to my mind:

* AFAIK macro-blocks are smaller in Theora than they are in MPEG4.
  Theora is thus not as well-suited for HDTV content as MPEG4.

* What is Y4M, and how did you feed your Y4M-File into encoder_example?
  Are you sure that the Theora file and the MPEG4-File you created have
  the same chroma sampling?  Else it wouldn't be a fair comparison.
  Actually I doubt that Theora and MPEG4 currently work with anything
  else than YUV12, but who knows...

BTW there is a hidden option in encoder_example that allows trading file
size for sharpness.  Might be a good idea to sacrifice some sharpness
for HDTV content.  Also you can increase the keyframe distance.  I
attach the patch of my local copy of encoder_example.c, that was "tuned"
that way.


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