Transcoding Settings

Scenarios

Audio and video distributed by VOD may be referenced by product websites and video websites or be played on devices like PCs and smartphones. VOD provides transcoding to change the audio/video encoding format, container format, resolution, and bitrate to adapt to different scenarios, devices, and network environments.

The transcoding function helps you achieve:

• Compatible with different devices. You can transcode the source audio/video into formats such as MP4 for playback on a wide range of devices.
• Adaptation to different network environments. You can set the output bitrate based on the network bandwidth.
• Low distribution costs. H.265 codec and low-bitrate HD can reduce the bitrate by about 20% without changing the resolution, thereby reducing media file distribution costs.
• HLS encryption. You can enable HLS encryption during transcoding to prevent secondary distribution if a media file is stolen.
• Copyright protection. You can add watermarks such as logos to your video.
• Audio extraction. Audio files can be extracted during transcoding. This function is used for those requiring audio only, such as radio stations and audio apps.
• Video extraction. You can disable audio and output video only.

Transcoding Template Introduction

If you are familiar with audio/video parameters and system templates cannot meet your requirements, you can create a transcoding template.

Notes

• Input audios/videos of the following formats can be transcoded:
  • Supported input audio formats: MP4, TS, MOV, FLV, MPG, MXF, WMV, ADTS, AVI, MKV, MPEG, VOB, RM, and MTS
  • Supported input video codecs: H.264, H.265, MPEG-2, MPEG-4, MJPEG, WMV1/2/3, and ProRes 422
  • Supported input audio codecs: AAC, AC3, EAC3, HE-AAC, MP2, MP3, PCM (s16le, s16be, s24le, s24be, DVD), and WMA
• To retain transcoded outputs of different formats, you need to submit a service ticket.

Editing a System Template

A system template has common parameters such as video resolution and codec preconfigured. Before using a system template, you are advised to check whether the settings of the system template meet your requirements. If the settings do not, you can edit the system template.

1. Log in to the VOD console.
2. In the navigation pane, choose Global Settings > Transcoding Templates.
3. Find the desired system template and click Edit. On the page displayed, modify template parameters.

   The editable parameters vary depending on system templates.

   • System template (system_template_group)

     You can change the video quality, container format, video codec, and watermark template, and enable low-bitrate HD and encryption. Video Quality has six options: LD, SD, HD, UHD, 2K, and 4K, as shown in Table 3.

     Figure 1 System template
     
   • Container template (original_template_group)

     You can change the format from FLV/HLS to MP4, or from MP3/MP4/FLV to HLS.

     Figure 2 Container template
     
   • Adaptive template (adaptive_template_group)

     Video codec can only be H.264. You can change the resolution. If the resolution is not set, the input resolution is used by default. After enabling low-bitrate HD, you can use video enhancement.

     Figure 3 Adaptive template
     

4. Click OK.

Creating a Template Group

If the preset templates cannot meet your requirements, you can create a template based on your needs. To customize an audio transcoding template, select MP3 or ADTS for Output Format.

1. Log in to the VOD console.
2. In the navigation pane, choose Global Settings > Transcoding Templates.
3. Click Create Custom Template Group. In the dialog box displayed, specify related parameters.
4. Set Basic Information by referring to Figure 4 and Table 1.
   Figure 4 Setting basic information
   

   Table 1 Parameters

   Parameter	Description
   Name	A template name can contain a maximum of 128 characters in letters, underscores (_), and digits. Example: MP4_H264
   Description	Description of a custom template.
   Output Format	Supported video formats: MP4, HLS, DASH_HLS, and DASH Supported audio formats: ADTS and MP3 Note: If an audio format is selected, video parameters are disabled.
   Package Format	Video container format. This parameter is available only when Output Format is set to HLS or DASH_HLS. Options: TS FMP4
   Segment Duration (s)	HLS segment length. This parameter is available only when Output Format is set to HLS or DASH_HLS.
   Different Segment Durations	Whether to enable variable-length segmentation, which controls playback startup time after transcoding. This parameter is available only when Output Format is set to HLS or DASH_HLS. If this function is enabled, you also need to set the following parameters: Initial Short Segments: specifies the number of segments before a video starts to play. The value is an integer ranging from 1 to 10. Short Segment Duration: specifies the duration of each initial short segment. The value is an integer ranging from 1 to 10, in seconds. After these parameters are configured, playback can start more quickly.
   Maximum I-Frame Interval	Maximum I-frame interval. The value ranges from 1 to 10, in seconds. Default value: 5
   Encryption	Whether to encrypt output media files. Input audio/video files are not encrypted. This parameter is available only when Output Format is set to HLS. That is, only HLS audio/video files can be encrypted and output. Before enabling this function, obtain the key URL by referring to HLS Encryption Settings.

5. Configure Video Parameters by referring to Figure 5 and Table 2.
   Figure 5 Video parameters
   
   

   If Audio only is selected, the output files do not contain any video information. Use this option to extract audio from a video file. Then perform 7 to configure audio parameters.

   Table 2 Video parameters

   Parameter	Description
   Video Codec	H.264 and H.265 are available.
   Transcode level	Video encoding quality level. Options: Default: The default mode is used. Speed: Efficiency is prioritized. High quality: Transcoded video quality is prioritized.
   Frame Rate	Number of frames displayed per second. The value is an integer ranging from 0 to 75. If the value is set to 0 or 1, the transcoded and input videos have the same frame rate.
   Low Bitrate HD	Whether to enable low-bitrate HD. Low-bitrate HD means achieving the same image quality with a lower output bitrate. If this function is enabled, the transcoding fee will be charged based on the low-bitrate HD standard. For details, see VOD Pricing Details.
   Upsample	Enabling this function improves video resolution and increases the number of sampling points.
   Watermark Template	Select the default watermark template or a custom watermark template. Select Default to use the default watermark template set in Watermark Settings. Select a custom watermark template to be used during transcoding.
   Stream Name	Stream name of a transcoded video.
   Quality	Video quality. The options are 4K, 2K, UHD, HD, SD, and LD.
   Resolution (Width x Height)	The default value is the recommended resolution for your selected video quality. You can change it based on your needs. If the width or height is set to 0, the side set to 0 is scaled in proportion to the other side. When the width is 0 and the height is not, the width is scaled proportionally. When the height is 0 and the width is not, the height is scaled proportionally. If both the width and height are 0, the transcoded file uses the resolution of the input file.
   Bitrate	The default value is the recommended bitrate for your selected video quality. You can change it based on your needs. If the bitrate is set to 0, the recommended bitrate for your input file is used for output.

   

   • There can be up to six outputs at different resolutions.
   • If you change the default resolution for an output stream, you are billed based on the configured resolution. For details, see VOD Pricing Details.

   You are advised to use the recommended resolutions and bitrates. For details, see Table 3.

   Table 3 Recommended resolutions and bitrates

   Video Quality	Recommended Resolution	Recommended Bitrate for H.265 (kbit/s)	Recommended Bitrate for H.264 (kbit/s)
   4K	3840 x 2160	5,600	8,000
   2K	2560 x 1440	4,900	7,000
   UHD	1920 x 1080	2,100	3,000
   HD	1280 x 720	700	1,000
   SD	854 x 480	500	600
   LD	480 x 270	200	300

6. Configure Audio Parameters by referring to Figure 6 and Table 4.
   Figure 6 Audio parameters
   
   

   If Video only is selected, the output file does not contain any audio information. This option is used for video extraction from a media file.

   Table 4 Audio parameters

   Parameter	Description
   Audio Codec	Audio codec. AAC and HEAAC1 are available. The default value is AAC.
   Audio Channel	Number of audio sources during audio recording or number of speakers during audio playback. Stereo and Mono are available. The default value is Stereo.
   Sampling Rate	Number of times per second that the audio signal is sampled. AUTO, 22050, 32000, 44100, 48000, and 96000 are available. The default value is AUTO, and the unit is Hz.
   Bitrate	Bitrate of an output audio, in kbit/s. The value is 0 or an integer ranging from 8 to 1,000. If this parameter is set to 0, the audio bitrate is an adaptive value. As a result, the audio bitrate of the transcoded file may be greater than that of the input video. So set this parameter to a proper value other than 0. CAUTION: If the audio bitrate is set too high when the source file is transcoded to HLS, a black screen will be displayed during playback on iOS devices. You are advised to customize a transcoding template and set a lower audio bitrate to ensure that the audio-to-video bitrate ratio is 1:3.
   Audio track separation	If the audio track file needs to be separated from the video file, toggle on this switch. This function is applicable only to HLS. The audio in the transcoded file is stored separately. NOTICE: The Audio track separation and Customize the primary index file options are mutually exclusive. You can configure only one of them.

7. Customize the primary index file, as shown in Figure 7. Table 5 describes the parameters you need to configure.
   

   • If Disable the file name extension of the primary index is selected, you do not need to set the parameters.
   • You can customize the primary index file only when Output Format is set to HLS.
   • The Audio track separation and Customize the primary index file options are mutually exclusive. You can configure only one of them.
   Figure 7 Customizing the primary index file
   

   Table 5 Parameters for customizing the primary index file

   Parameter	Description
   Suffix of the primary index file	The name of the primary index file is index_{suffix}.
   Select Stream	By default, the drop-down list displays all stream names added. Select one or more stream names as required.

8. Click OK.

   You can view the created template on the Transcoding Settings page.

Editing or Deleting a Custom Template

After a custom template is created, you can click Edit in the template list to modify the template. You can also click Delete to delete templates that you no longer need. If a template is deleted, audio/video using this template will not be deleted.

Figure 8 Editing a custom template