After you enable the audio extraction feature, Alibaba Cloud CDN points of presence (POPs) extract audio data from a video file and return only the audio data to clients. This reduces bandwidth and traffic usage. This topic describes how to enable the audio extraction feature.
Background information
When a client requests a video file, the client sends a request to the nearest CDN node. The request contains the URL of the video file, for example, http://www.aliyun.com/test.flv?ali_audio_only=1. Then, the CDN node returns the audio data extracted from the video file to the client. The client must support the following transmission method: Transfer-Encoding: chunked.
The audio extraction feature does not support range requests. Browsers such as Safari initiate a range request when a user plays a video. We recommend that you provide user-developed clients to your users for extracting audio data.
To allow users to drag the progress bar during audio playback, you must also configure the video seeking feature. When a user drags the progress bar, the system reads the metadata of the source video file to retrieve the playback duration. This duration is used to implement seeking. For more information, see Video seeking.
Audio extraction does not support MP4 files whose box header size is 16 (64 bits). It only supports MP4 files whose box header size is 8.
Procedure
Log on to the ApsaraVideo VOD console.
In the left-side navigation pane, choose Configuration Management > CDN Configuration > Domain Names.
On the Domain Names page, find the domain name that you want to manage and click Configure in the Actions column.
In the navigation pane on the left, click Video Related.
In the Listen to Video area, turn on the switch.
After you enable the audio extraction feature, you must use the
ali_audio_onlyrequest parameter. The supported file formats are listed in the following table.File format
Metadata
ali_audio_only
Example
MP4
The metadata of a video file on the origin server must be contained in the file header and cannot be contained in the file tail.
Set the
ali_audio_onlyparameter to 1 to require Alibaba Cloud CDN to return only the metadata and audio data of the requested video file. The video data is not returned. If requests do not include this parameter or it is set to other values, audio extraction is not performed.http://domain/video.mp4?ali_audio_only=1.FLV
No requirements.
Set the
ali_audio_onlyparameter to 1 to require Alibaba Cloud CDN to return only the metadata and audio data of the requested video file. The video data is not returned. If requests do not include this parameter or it is set to other values, audio extraction is not performed.http://domain/video.flv?ali_audio_only=1.