Encoding Requirements and Recommendations
7.When encoding files, annotate and store notes on the audio levels of both the source tape and input settings of the encoder. It will then be possible to verify audio levels of later encoding sessions. 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 is available from previously encoded files, compare the files. When possible, measure audio levels of the source tapes and of the encoded files. At a minimum, listen to and compare files. Even if encoding is done at the same production facility, variances between sessions may occur. 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.
8.MPEG files are constructed from intertwined (i.e. multiplexed) audio and video streams. The length of video and audio stream segments within MPEG files should be identical if possible.
Ending the audio segment at a .5 second interval (i.e., at an “I- frame”) will ensure identical stream lengths, providing smooth and seamless looping playback.
9.When encoding SMPTE tracks it is recommended to encode these tracks
10.Standard color bars and audio test tones: MPEG files may be encoded along with the content or source files for reference and calibration. These encoded display test/tuning files should be separate
11.To play back still images or
Multiplexing a blank audio track on all video only MPEG files is highly recommended.
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