Dolby Laboratories DM100 Instrukcja Użytkownika Pobierz pdf (Strona 22)

Dolby Model DP583 Frame Synchronizer User’s Manual Applications

3-2

1 / frame rate

Dolby E FrameDolby E FrameDolby E Frame

Video Frame Video Frame Video Frame

guard band

Figure 3-1 Phase Aligned Dolby E Frames

Figure 3-2 illustrates a misaligned Dolby E bitstream with respect to video. Notice the

guard band location has been “offset” in time so that Dolby E data is present at the

defined switch point. This scenario will result in the loss of data during a switch or an

edit of the Dolby E stream and thus would require the use of the DP583 Frame

Synchronizer to re-align the Dolby E frames, as in Figure 3-2.

1 / frame rate

Video Frame Video Frame Video Frame

Dolby E FrameDolby E FrameDolby E Frame... Frame

guard band

Figure 3-2 Non-Phase Aligned Dolby E Frames

3.2 Dolby E Post Production Application

In some postproduction applications, it is desirable to process audio and video separately.

The audio is often recorded on an audio-only medium, such as DAT, Digital multitrack

tape, or a Digital Audio Workstation. In the case of Dolby E audio, this presents a

problem because the phase and clock relationship between the video reference and the

Dolby E audio frames is lost with the transfer to an audio-only medium.

The DP583 Frame Synchronizer can be used to re-lock the Dolby E audio to the

video reference, repairing the damaged phase relationship. It is recommended that

both the audio playback device and the DP583 be locked to the same reference, as

shown in Figure 3-3. This prevents the DP583 from having to synchronize the data

from one clock domain to another, which can cause lip-sync errors as the DP583

varies its delay during the synchronization process.

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