Transcoding is an essential part of media processing. This topic describes the supported transcoding methods and how to use transcoding in ApsaraVideo VOD.
Before you start
Before you start transcoding, make sure that you understand basic concepts such as encoding format, container format, bitrate, and resolution. For more information, see Bitrate.
What is transcoding?
Video transcoding refers to the process of converting a compressed video stream to another video stream to adapt to different network bandwidths, terminal processing capabilities, and user requirements. Transcoding is a process in which decoding and encoding are performed. Streams before and after transcoding may use the same or different video encoding standards.
The following figure shows the point at which video transcoding is performed in a video production workflow.
Features
Video processing: ApsaraVideo VOD provides comprehensive transcoding and container format conversion capabilities to convert to various media file formats.
Audio processing: ApsaraVideo VOD provides audio processing features such as audio transcoding and audio extraction.
Watermarking: ApsaraVideo VOD supports static watermarks, animated watermarks such as GIF and MOV files, and text watermarks. You can add multiple watermarks to a video. For more information, see Video watermarks.
Multiple preset definitions: ApsaraVideo VOD provides multiple preset definitions, such as Standard Definition, High Definition, Ultra High Definition, 2K, and 4K. ApsaraVideo VOD provides recommended optimal settings to help you start transcoding without the need for technical understanding.
Multi-scenario solutions such as audio extraction: You can extract an audio track of the standard or high quality from a video as an audio output. This is suitable for scenarios such as broadcasting at a radio station.
Content protection: ApsaraVideo VOD supports content encryption for various scenarios such as online education and copyright protection.
Scenarios
Compatibility with multiple terminals: The generated content can be played on PCs, TVs, and mobile devices.
Adaptation to multiple network environments: ApsaraVideo VOD allows you to select the most appropriate bitrate based on your network bandwidth for smooth playback.
Low storage and distribution costs: You can change video bitrates, increase the compression rate, and reduce file sizes without changes to image quality. This ensures smooth playback and reduces storage and traffic costs.
Content protection: Content encryption is supported for various scenarios such as online education and copyright protection.
Watermarking: You can add information such as enterprise logos, TV station logos, user IDs, and nicknames as watermarks for video copyright declaration or brand promotion.
ApsaraVideo VOD provides multiple scenario-specific preset definitions and streamlines the process from uploading to transcoding based on long-term analysis of large volumes of data.
Transcoding methods
ApsaraVideo VOD supports multiple transcoding methods. You can select transcoding methods based on your business requirements.
Transcoding method | Description | Scenario | |
Standard transcoding | Regular video transcoding | ApsaraVideo VOD provides the following seven preset video definitions: Low Definition, Standard Definition, High Definition, Ultra High Definition, 2K, 4K, and Original. | Regular video transcoding can meet your basic transcoding requirements. You can generate videos in different specifications that can be played in different network environments or on different devices and use Alibaba Cloud CDN to accelerate the distribution. Regular transcoding is suitable for scenarios such as asynchronous processing and delayed playback. |
Audio transcoding | ApsaraVideo VOD provides two audio quality options: Standard Quality and High Quality. | Audio transcoding is suitable for scenarios in which you want to improve the audio quality. | |
Container format conversion (original quality) | Container format conversion only converts the container format of videos and does not change the definition and bitrate. | This transcoding method is suitable for scenarios in which you do not need to change the image size or bitrate of the video. | |
Narrowband HD transcoding | Narrowband HD TM 1.0 | Based on the proprietary transcoding technology of Alibaba Cloud, Narrowband HD™ 1.0 analyzes each scene, action, content, and texture in videos. This reduces the bitrate and bandwidth costs without changes to image quality. For more information, see the article posted in Yunqi Community. |
|
Narrowband HD TM 2.0 | Narrowband HD TM 2.0 attempts to reduce the bitrate according to the definition expectation, and selects the best resolution according to the preset bitrate. This technology is developed based on the human vision model and emphasizes user experience over fidelity for video optimization. Because of the Alibaba Cloud algorithm applied in this feature, Narrowband HD™ 2.0 performs better than current video encoders and enhances video clarity at lower bitrates. Compared with the Narrowband HD TM 1.0, Narrowband HD™ 2.0 delivers higher video resolution at lower bitrates. Note Narrowband HD TM 2.0 is available only in the China (Shanghai), China (Beijing), China (Shenzhen), and Singapore regions. | This transcoding method is suitable for videos whose original quality is relatively low. | |
Distribute without transcoding | No Transcoding template group (preset) | Videos are directly played in original quality without transcoding.
| The No Transcoding template group is suitable for scenarios in which you can directly play videos in original quality, such as short videos and live-to-VOD recording. This reduces the response time of playback requests and transcoding costs.
|
Adaptive bitrate stream transcoding | Video packaging transcoding | You can use a video packaging template to transcode a video into video streams at different bitrates in the HTTP-Live-Streaming (HLS) format, and package these video streams into a file. This allows media players to switch to the most appropriate video stream based on the network bandwidth. The adaptive bitrate switching feature supports automatic definition switching based on the network environment. You can also manually switch the definition. | This transcoding method is suitable for adaptive bitrate streaming. |
Subtitle packaging transcoding | You can use a subtitle packaging template to configure subtitles for a video and store the subtitle information in the adaptive bitrate streaming file. This allows media players to switch between subtitles. | This transcoding method is suitable for subtitle switching in multiple languages. | |
Billing
You are charged for transcoding based on the specification ad duration of the transcoded video. For more information, see Media transcoding.
Usage notes
You are charged for each transcoding job. A new video file is generated after a transcoding job is complete. To improve storage utilization and prevent additional charges, we recommend that you create transcoding template groups and transcoding jobs based on your business requirements.
For more information about the supported formats of input and output files, see Limits on media transcoding.