Visual Circuits Mantis MC, User Manual

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Encoding Requirements and Recommendations
17
6. Although the Mantis can transcode NTSC and PAL, it is
recommended to encode to the video standard (NTSC or PAL)
that the Mantis is set to display.
7. When encoding files, annotate and store notes on the audio
levels of both the source tape and input settings of the encoder.
This permits verifying the audio levels of later encoding
sessions.
8. MPEG files are constructed from intertwined
(i.e. multiplexed) audio and video streams. If possible, the
length of the video and audio stream segments within the
MPEG files should be identical. Ending the audio segment at
a .5 second interval (i.e., at an “I-frame”) ensures identical
stream lengths and results in smooth and seamless looping
playback.
9. It is recommended that SMPTE tracks should be encoded as
hot , at approxi6db.
This adjustment compensates for some SMPTE information
that may be lost during compression. Sample testing should be
done with all SMPTE tracks because not all encoders respond
in the same way.
10. For reference and calibration, encode into the MPEG files the
standard color bars and audio test tones along with the content
or source files. These encoded display test and audio tuning
files should be separate files, not headers or footers of the
presentation.
Even if encoding is done at the same production facility,
variances between sessions may occur and once MPEGs are
encoded, the audio level of a file cannot be changed unless
the file is re-encoded or a new audio track is mixed.
Thus, it is desirable to maintain a baseline audio level across
all files of a presentation whether at single or multiple
locations. If no encoding notes or data are available from
previously encoded files, compare the files. When possible,
measure the audio levels of the source tapes and of the
encoded files. At a minimum, listen to and compare the files.