Topics covered in this article:
- The MP4 export function
- Exporting an MP4 file
The Dolby Atmos Renderer allows the user to export an MP4 file for quality control (QC) playback on consumer devices and other use cases.
MP4 files are exported from an open master file (48kHz only).
The exported MP4 files contain a video and audio track:
- The video track in the MP4 file is black video at 720p resolution and 24fps encoded with the h264 video codec. This frame rate is independent of the frame rate of the open master file. The video track is included because many media players will not play an audio-only MP4 file.
- The audio track is encoded from the open Master File
- The Music encoding mode encodes a Dolby Digital Plus JOC file at a bit rate of 768kbps using the Music Light Dynamic Range Control profile.
- The Film encoding mode encodes a Dolby Digital Plus JOC file at a user selectable bit rate of 448kbps or 768kbps using the Film Light Dynamic Range Control profile.
The primary use case for the MP4 export is an audio-only QC of the encoded Dolby Atmos mix on consumer playback equipment, e.g., audio/video receiver (AVR) or Soundbar. A few examples of how this can be done are:
- Transferring the MP4 file to a USB flash drive and playing back via a Blu-ray player with the audio set to bitstream passthrough.
- Playback from Safari Browser Airplayed to an Apple TV 4k
The MP4 file can also be played back in the Dolby Reference Player application.
The MP4 can also be used as the audio master for packaging streaming media.
Exporting an MP4 File
To export an MP4 file:
- Load a master file (48kHz only).
- From the menu bar, navigate to File > Export MP4 or type Command+Shift+M (Mac) or Control+Shift+M (Windows).
- Choose an output directory.
- Enter a file name.
- Select which Dynamic Range Control profile to use based on the type of content.
- If using Film mode, choose between a bit rate of 448kbps or 768kbps (default).
- Select Entire Master or Set Manually to use an In and Out point. This is helpful for removing unnecessary pre and post-roll.