Encoding_MultiChannel_Audio

topic	languages	products	description
sample	javascript,typescript	azure-media-services	This sample demonstrates how to create an encoding Transform that encodes multi channel audio to 5.1 outputs and stereo.

Encoding for multi-channel audio with channel mapping Preset

This sample demonstrates how to create an encoding Transform that uses channel mapping and audio track selection from the input source to output two new AAC audio tracks. The standard encoder is limited to outputting 1 Stereo track, followed by a 5.1 surround sound audio track in AAC format.

In this example we input an audio only source file with the following track layout of discreet audio tracks. The file is named "surround-audio.mp4" in the project folder.

1. Left stereo
2. Right stereo
3. Left front surround
4. Right front surround
5. Center surround
6. Low frequency
7. Back left
8. Back right

We then create a list of TrackDescriptor type to allow us to selectively map the audio tracks from the input source file into a specific Channel on the output. The order of these are important when output to the Transform next below.

                var trackList = new List<TrackDescriptor>
                {
                       new SelectAudioTrackById()
                        {
                            TrackId = 1,
                            ChannelMapping = ChannelMapping.StereoLeft
                        },
                        new SelectAudioTrackById()
                        {
                            TrackId = 2,
                            ChannelMapping = ChannelMapping.StereoRight
                        },
                        new SelectAudioTrackById()
                        {
                            TrackId = 3,
                            ChannelMapping = ChannelMapping.FrontLeft
                        },
                        new SelectAudioTrackById()
                        {
                            TrackId = 4,
                            ChannelMapping = ChannelMapping.FrontRight
                        },
                        new SelectAudioTrackById()
                        {
                            TrackId = 5,
                            ChannelMapping = ChannelMapping.Center
                        },
                        new SelectAudioTrackById()
                        {
                            TrackId = 6,
                            ChannelMapping = ChannelMapping.LowFrequencyEffects
                        },
                        new SelectAudioTrackById()
                        {
                            TrackId = 7,
                            ChannelMapping = ChannelMapping.BackLeft
                        },
                        new SelectAudioTrackById()
                        {
                            TrackId = 8,
                            ChannelMapping = ChannelMapping.BackRight
                        }
                };

A Transform is then created to generate the Stereo and 5.1 surround sound tracks from the track descriptor list. The first two tracks in the track descriptor list will be output to the Stereo AAC output defined as 2 channels in the Transform. The remaining 6 tracks will go into the second AAC output defined in the transform as using 6 channels.

                  new TransformOutput(
                        new StandardEncoderPreset(
                            codecs: new Codec[]
                            {
                                // Add an AAC Audio layer for the audio encoding of the Stereo tracks to be mapped to.
                                new AacAudio(
                                    channels: 2, // stereo track
                                    samplingRate: 48000,
                                    bitrate: 128000,
                                    profile: AacAudioProfile.AacLc
                                ),
                                 new AacAudio(
                                    channels: 6, // 5.1 surround sound track 
                                    samplingRate: 48000,
                                    bitrate: 320000,
                                    profile: AacAudioProfile.AacLc
                                ),

After encoding, you will be able to playback the asset in the Azure Media Player and select from two track options. One stereo track and one 5.1 surround sound AAC track.

.env

Use sample.env as a template for the .env file to be created. The .env file must be placed at the root of the sample (same location than sample.env). Connect to the Azure portal with your browser and go to your media services account / API access to get the .ENV data to store to the .env file.