Aaron Heller wrote:
Problem solved. Here's the YouTube version of one of the most downloaded
file from Ambisonia, AJH_eigtht_positions.amb
https://youtu.be/eY9DMn8pgGA
Thanks to Albert, Dillon, Bruce, and Marc for suggestions. Dillon
diagnosed the problem, but it took a while to discover that the fix had to
be applied farther upstream in my processing chain.
TL:DR: use a plain old WAV_PCM file for the audio input to FFMPEG, not a
WAVE-EX file.
I am using the remix effect in SOX to convert from AMB format to ACN/SN3D
-- "remix -m 1 3v0.7071 4v0.7071 2v0.7071". When sox writes out a
4-channel file it defaults to WAVE-FORMAT-EXTENSIBLE (which is correct
according to the MS standards) with the channel mask set to "quad". I don't
see anyway to change that to 4.0.
Here's the problem .... when writing a video file, FFMPEG appears to use
the channel_mask from the audio file even if a different channel_mask is
specified on the command line. So even when I specified "-channel_layout
4.0", the resulting MOV file still had the channel layout set to "quad",
which was then rejected by YouTube.
The workaround is to use the option "-t wavpcm" to force SOX produce a
plain old WAVPCM file. (note that use of WAVPCM for more then 2 channels
is undocumented). As a belt-and-suspenders measure, I added
"-guess_layout_max 0" to the input in FFMPEG.
I wrote a Python script that automates the whole process from AMB to MOV
with spatial metadata. You can find it here:
https://bitbucket.org/ambidecodertoolbox/amb2yt/src/master/amb2yt.py
--
Aaron Heller (hel...@ai.sri.com)
Menlo Park, CA US
Well done.
Just one suggestion: As VR is a lot about 3D, you could think about to
extend the "8 positions" demo to some equivalent 3D demo. Which probably
would be "26 positions". (3 rings w/ 8 positions each at -45º, 0º and
45º elevation. 2 additional positions at +-90º, i.e. zenith/nadir.)
Stefan
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