There are many reasons for audio-only streams. Perhaps you are sending radio or podcasts, where the main content is audio, and video is only a secondary interest. Setup for filming and sending the video adds extra expense and effort, and may not offer enough to be worthwhile. Or you may be sending audio and video, but are interested in offering and audio-only option for some viewers.
It is rather noteworthy that audio quality and service is more important than the video for many types of streaming content. A large portion of streaming is primarily focused on the host speaking, rather than seeing what they are doing. When your content is someone talking on a topic, or a group of people engaging in dialog, the video content quickly becomes a secondary matter. This sort of content is also more engaging to a group of viewers who may not be sitting in front of a screen. Many people enjoy listening to podcasts or other talk content while mowing their lawn, driving to work, or exercising, when actually watching the video is impossible.
ScaleEngine offers a number of services that can help you offer the best experience to your audience, even when their wants are quite varied: we support direct audio-only feeds, as well generating audio only streams from video content.
ScaleEngine does live transcoding that will output various lower bitrates and frame sizes, as well as an audio only feed. We can offer a copy of the original audio track for viewers who are only listening, or generate a lower-bitrate audio rendition for viewers on bandwidth constrained connections. Generally speaking this is the best option if you are running a podcast and want a lower bandwidth option for your audience, who may be driving or not looking at the screen, and do not benefit from the video portion. Not needing to load the video data will improve performance and reliability over cellular connections, not to mention saving you and your viewers bandwidth fees.
It's important to remember that an audio option needs to be independent of the video player. Video players on many devices do not handle switching from a track with video to one without, and will not behave well if audio only is present and selected by the audience member on their device.
ScaleEngine specializes in transcoding "odd" audio codecs to the industry standard AAC, which is especially useful in the case of installed cameras, which often use GPP and MP2 audio formats. These have to be transcoded to AAC to be usable on the modern device. There is also WebRTC, which uses OPUS - completely incompatible with an HLS feed (unless transcoded to AAC).
We encourage you to test our streaming system free here.
FFMpeg can be used to send an audio-only stream. An example of settings that work to stream a file to our systems:
ffmpeg -re -i test.flac -vn -c:a aac -b:a 96k -f flv rtmp://user-origin.secdn.net/user-origin/live/stream
Any source can be used, as long as you ensure the settings you are sending with are correct. Make sure the audio is AAC or MP3, and the container format is FLV.
If you are sending from a pre-recorded file, the -re flag makes it send
the stream in 'real time', rather than as fast as it can. Do not use it if your source is already
a stream.