Tech Tip - Creating Transport Streams with SMPTE-302 PCM Audio


All current PixelTools products can create streams with 8 or 2 channel PCM audio multiplexed into a transport stream in compliance with delivery specifications for Netflix, DirecTV and many other VOD systems.

Encoding video content with PCM Audio


MPEGRepairHD and Expert-HD can encode high quality video from a variety of sources. Expert-Broadcast can encode video from the Adobe Premiere timeline. All three tools can be set up to multiplex two or eight PCM audio channels with the encoded video into a SMPTE-302 transport stream.

You need to have your audio channels available before starting the encoding. The audio can be a single stereo (2 channel) .wav file, 8 audio channels consisting of a single stereo (2 channel) .wav file and 6 discreet (1 channel) .wav files or an 8 channel .wav file.

Don’t forget to include enough bandwidth in the transport output bit-rate to include the 2 or 8 PCM audio channels.

Two Channel PCM Audio


Launch MPEGRepairHD, set up your video encoding specifications and select Optimize Encoder Configure | Audio/Mux dialog.  Select the “Mux uncompressed audio file” radio button and browse for your 48 khz 16 bit per sample stereo .wav file as below:

PixelTools MPEGRepairHD

Click to see larger view

Depressing the Encode Run button will cause your source frames to be encoded and then your selected audio multiplexed in a SMPTE 302 transport stream.

Eight Channel PCM Audio


Netflix and other content providers that we work with specify consistent 8 audio channel assignments.  Channel numbers 7 and 8 are used for the stereo audio pair with 7 being the left and 8 being the right.  Channel numbers 1 through 6 are used for the surround sound channels as follows:

1. Left
2. Right
3. Center
4. LFE
5. Left Surround
6. Right Surround

 

You can use an 8 channel ..wav file with the above channel assignments. Browse for this 8 channel .wav file in the Mux Audio from Uncompressed File edit box as detailed above. MPEGRepairHD will detect the 8 channel audio file and multiplex the channels into a SMPTE 302 Transport file.

You can also use a stereo .wav file and 6 single channel .wav files.  The files must be named properly for MPEGRepairHD to recognize the discrete channels. The stereo .wav file can have any name. Each of the single channel .wav files must have names that end with _1.wav, _2.wav through _6.wav where the numbers in the names correspond with the above delivery channel assignments.

Select the stereo .wav file in the Mux Audio from Uncompressed File edit box as detailed above. MPEGRepair will look for appropriately named discrete file names to determine whether the video will be multiplexed with two or eight audio channels.

  
A valid set of files can be named

AudioTrack.wav (stereo pair)
AudioTrack_1.wav
AudioTrack_2.wav
AudioTrack_3.wav
AudioTrack_4.wav
AudioTrack_5.wav
AudioTrack_6.wav



Multiplexing of video with PCM audio into SMPTE 302 Transport streams

 

MPEGRepairHD or Expert-HD, Expert-Caption and Expert-Mux can be used to multiplex existing elementary MPEG video with 2 or 8 audio channels. In MPEGRepairHD, select the Encode  Configure | Audio/Mux  “No Encode; Mux Only” option.  Browse for your PCM audio file(s) as detailed above in the “Mux audio from uncompressed file” Select your elementary encoded video in the GUI Encode Input edit box and enter a name for your file output in the Encode Output edit box. Depressing the Run button causes the tool to multiplex the input video with the audio .wav files.

PixelTool MPEGRepairHD

Click to see larger image

Expert-HD and Expert-Caption include an equivalent dialog to enable multiplex of PCM audio with pre-encoded video into a SMPT-302 stream Transport.


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MPEGRepairHD, Expert-HD, Expert-Caption and Expert-Broadcast are trademarks of PixelTools Corporation. All other brand names are trademarks or registered trademarks of their respected holders.


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