原文链接

杜比全景声渲染器的.mp4导出功能旨在提供一个可以在消费设备上播放的mp4文件，例如蓝光播放器／支持杜比全景声的AVR或支持Atmos的Soundbar

.mp4文件中包含带有杜比全景声内容的Dolby Digital Plus 码流（.ec3），以及等长的分辨率为1280x720，帧率与载入的Dolby Atmos母版文件匹配的视频（h.264）。

用户可选择配置文件进行音频编码：Film 或 Music

  • Film Proile

    • 码率：448kbps或768kbps（用户可选）
    • 动态范围控制参数（Dynamic Range Control Profile）：Film Light
    • Dialnorm元数据值：测量算法为带有Dialog Intelligence（对白智能）的ITU 1770-4标准，语音阈值为15%

  • Music Profile

    • 码率：768kbps
    • 动态范围控制参数（Dynamic Range Control Profile）：Music Light
    • Dialnorm元数据值：测量算法伟ITU 1770-4标准

注意：下变换模式(Downmix Mode)及自定义衰减(Custom Trim)将在编码阶段应用

注意：Dialnorm元数据值是作为编码过程的一部分在.ec3的基本码流（elementary stream）中设置的。为了确认符合交付要求，可以从响度分析窗口中使用内部的离线响度表，或使用Nugen、iZotope的相关工具对5.1 re-render进行响度测量。

What is in the .mp4 export and how are these encoded?

The .mp4 export function is designed to provide an mp4 file that can playback on a consumer device like a Blu-Ray player/Atmos enabled AVR or an Atmos enabled soundbar.

The .mp4 contains a Dolby Digital Plus with Atmos Content bitstream (.ec3) and matching duration black video at 1280x720 resolution at the framerate of the loaded Atmos master file (.h264).

The audio is encoded with a user selectable profile: Film or Music

Film encodes the audio to Dolby Digital Plus with Atmos Content:
Datarate: 448kbps or 768kbps (user selectable)
Dynamic Range Control Profile: Film Light
Dialnorm metadata value: set per measurement with ITU 1770-4 with Dialog Intelligence with a speech threshold of 15%

Music encodes the audio to Dolby Digital Plus with Atmos Content:
Datarate: 768kbps
Dynamic Range Control Profile: Music Light
Dialnorm metadata value: set per measurement with ITU 1770-4

Note: downmix mode and custom trim values are used during the encode.

Note: the dialnorm metadata value is set in the .ec3 elementary stream as part of the encoding process. Loudness measurement to confirm compliance with delivery specifications should use internal offline loudness measurement from the Loudness Analysis window or use the loudness specific 5.1 re-render for loudness measurement with product from Nugen, Izotope etc.