Video transcoding enables the transformation of media files by altering encoding formats, adjusting resolution and bitrate, converting container formats, and enhancing overall video quality. This topic describes how to configure video transcoding parameters and includes practical examples.
Scenarios
Adaption to different terminal devices and network environments
You can adjust the frame rate and bitrate of a media file to ensure compatibility with various terminal devices and network environments.
Efficient encoding for reduced costs
Efficient encoding algorithms optimize media processing by lowering bitrates and minimizing playback stuttering while maintaining video quality. This approach reduces both storage and bandwidth costs.
Smart production technologies for video enhancement and reproduction
MPS enhances low-resolution videos to higher definition and generates new media files through watermarking, snapshot capture, or editing. These capabilities are powered by smart production technologies, including video AI, super-resolution, and advanced media processing.
Prerequisites
Intelligent Media Management (IMM) is activated. For more information, see Activate IMM.
The corresponding Object Storage Service (OSS) bucket is bound to an IMM project. For more information about how to bind an OSS bucket to an IMM project in the OSS console, see Get started. For more information about how to bind a bucket to an IMM project by using the IMM API, see AttachOSSBucket.
The IMM permissions are granted to your account. For more information, see Permissions.
Usage notes
Video transcoding supports only asynchronous processing (x-oss-async-process).
Video transcoding does not support anonymous access.
Video transcoding supports the following media formats: MP4, MPEG-TS, MKV, MOV, AVI, FLV, M3U8, WebM, WMV, RM, and VOB.
Video transcoding is a billable service, with media processing costs covered under the IMM usage fees. For more information, see Billable items.
Solution overview
Upload a video file to a bucket.
Create a media transcoding task.
Upon successful task execution, save the transcoded video file to OSS.
Parameters
Action: video/convert
The following table describes the parameters for video transcoding.
Parameter | Type | Required | Description |
ss | int | No | The start time of the video from which transcoding begins. Unit: milliseconds. Valid values:
|
t | int | No | The duration of video content to be transcoded after the specified start time. Unit: milliseconds. Valid values:
|
f | string | Yes | The type of the media container. Valid values:
|
vn | int | No | Specifies whether to disable video stream generation. Valid values:
|
vcodec | string | No | The encoding format of the video. Valid values:
|
fps | float | No | The desired frame rate. Valid values: 0 to 240. |
fpsopt | int | No | The frame rate option. Valid values:
|
pixfmt | string | No | The desired pixel format. By default, the desired pixel format matches the source pixel format. Valid values:
|
s | string | No | The desired resolution.
|
sopt | int | No | The resolution option. Valid values:
|
scaletype | string | No | The resizing mode. Valid values:
|
arotate | int | No | Specifies whether to enable adaptive resolution orientation. Valid values:
|
g | int | No | The keyframe interval. Valid values: 1 to 100000. |
vb | int | No | The desired video bitrate. Unit: bit/s. Valid values: 10000 to 100000000. |
vbopt | int | No | The video bitrate option. Valid values:
|
crf | float | No | The constant rate factor (CRF). Valid values: 0 to 51. |
maxrate | int | No | The maximum bitrate. Unit: bit/s. Valid values: 10000 to 100000000. |
bufsize | int | No | The buffer size. Unit: bit. Valid values: 10000 to 200000000. |
an | int | No | Specifies whether to disable audio stream generation. Valid values:
|
acodec | string | No | The encoding format of the audio. Valid values:
|
ar | int | No | The sampling rate of the output audio. Valid values:
|
ac | int | No | The number of sound channels in the output audio. By default, the output audio retains the same number of channels as the source audio. Valid values: 1 to 8. |
aq | int | No | The audio compression quality. This parameter and the ab parameter are mutually exclusive. Valid values: 0 to 100. |
ab | int | No | The desired audio bitrate. This parameter and the aq parameter are mutually exclusive. Valid values: 1000 to 10000000. |
abopt | int | No | The audio bitrate option. Valid values:
|
sn | int | No | Specifies whether to disable subtitle generation. Valid values:
|
adepth | int | No | The sampling bit depth of the output audio. Valid values: 16 and 24. Note This parameter takes effect only if you set the acodec parameter to flac. |
segment | string | No | The media segmentation settings. By default, segmentation is not applied. |
f | string | No | The media segmentation mode. Valid values:
Parent node: segment |
t | int | No | The length of the segment. Unit: milliseconds. Valid values: 0 to 3600000. Parent node: segment |
You may also need to use the sys/saveas and notify parameters in a video transcoding task. For more information, see sys/saveas and Message notification.
Use the OSS API
Convert AVI to MP4
Transcoding task information
Source object
Video format: AVI
Video name: example.avi
Processing method: Transcode the video.
Destination object
Video information
Video format: MP4
Video name: outobjprefix.mp4
Video stream format: H.265
Video resolution: 1920 × 1080
Video frame rate: 30 fps
Video bitrate: 2 Mbit/s
Audio information
Audio stream format: AAC
Audio bitrate: 100 Kbit/s
Subtitle stream: disabled
Output path: oss://outbucket/outobjprefix.mp4
Sample request
POST /example.avi?x-oss-async-process HTTP/1.1
Host: video-demo.oss-cn-hangzhou.aliyuncs.com
Date: Fri, 28 Oct 2022 06:40:10 GMT
Authorization: SignatureValue
// Transcode the example.avi object to the MP4 container format and specify H.265 as the video stream format. Set the resolution to 1920x1080, frame rate to 30 fps, and video bitrate to 2 Mbit/s. Specify AAC as the audio stream format and set the audio bitrate to 100 Kbit/s. Disable subtitle stream generation. Save the output object as oss://outbucket/outobjprefix.mp4.
x-oss-async-process=video/convert,f_mp4,vcodec_h265,s_1920x1080,vb_2000000,fps_30,acodec_aac,ab_100000,sn_1|sys/saveas,b_b3V0YnVja2V0,o_b3V0b2JqcHJlZml4LnthdXRvZXh0fQConvert from AVI to TS
Transcoding task information
Source object
Video format: AVI
Video name: example.avi
Processing method
Length to be transcoded: Transcode 60,000 milliseconds of the video, starting from the 1,000th millisecond of the video.
Segmentation: Create HTTP Live Streaming (HLS) segments at intervals of 30 seconds.
Transcoding completion notification: Send Simple Message Queue (SMQ, formerly MNS) messages.
Destination object
Video information
Video format: TS
Video stream format: H.264
Video bitrate: 1 Mbit/s
Audio information
Audio format: AAC
Audio bitrate: 100 Kbit/s
Output paths:
TS objects: oss://outbucket/outobjprefix-%d.ts
M3U8 object: oss://outbucket/outobjprefix.m3u8
Sample request
POST /example.avi?x-oss-async-process HTTP/1.1
Host: video-demo.oss-cn-hangzhou.aliyuncs.com
Date: Fri, 28 Oct 2022 06:40:10 GMT
Authorization: SignatureValue
// Transcode the example.avi video.
x-oss-async-process=video/convert,ss_10000,t_60000,f_ts,vcodec_h264,vb_1000000,acodec_mp3,ab_100000/segment,f_hls,t_30000|sys/saveas,b_b3V0YnVja2V0,o_b3V0b2JqcHJlZml4LnthdXRvZXh0fQ/notify,topic_QXVkaW9Db252ZXJ0Convert from AVI to MP3
Transcoding task information
Source object
Video name: example.avi
Video format: AVI
Processing method: Extract and convert audio.
Destination object
Audio container format: MP3
Audio coding format: MP3
Audio bitrate: 100 Kbit/s
Video stream: disabled
Subtitle stream: disabled
Output path: oss://outbucket/outobjprefix.mp3 (If the video contains multiple audio channels, only the first channel is processed by default.)
Sample request
POST /example.avi?x-oss-async-process HTTP/1.1
Host: video-demo.oss-cn-hangzhou.aliyuncs.com
Date: Fri, 28 Oct 2022 06:40:10 GMT
Authorization: SignatureValue
// Extract audio from the example.avi object and transcode the extracted audio.
x-oss-async-process=video/convert,f_mp3,acodec_mp3,ab_100000,vn_1,sn_1|sys/saveas,b_b3V0YnVja2V0,o_b3V0b2JqcHJlZml4LnthdXRvZXh0fQUse OSS SDKs
You can use OSS SDK for Java, Python, or Go to transcode videos in asynchronous mode.
Java
If you want to use OSS SDK for Java, make sure that the SDK version is V3.17.4 or later.
import com.aliyun.oss.ClientBuilderConfiguration;
import com.aliyun.oss.OSS;
import com.aliyun.oss.OSSClientBuilder;
import com.aliyun.oss.common.auth.CredentialsProviderFactory;
import com.aliyun.oss.common.auth.EnvironmentVariableCredentialsProvider;
import com.aliyun.oss.common.comm.SignVersion;
import com.aliyun.oss.model.AsyncProcessObjectRequest;
import com.aliyun.oss.model.AsyncProcessObjectResult;
import com.aliyuncs.exceptions.ClientException;
import java.util.Base64;
public class Demo {
public static void main(String[] args) throws ClientException {
// Specify the endpoint of the region in which the bucket is located.
String endpoint = "https://oss-cn-hangzhou.aliyuncs.com";
// Specify the ID of the Alibaba Cloud region in which the bucket is located. Example: cn-hangzhou.
String region = "cn-hangzhou";
// Obtain a credential from the environment variables. Before you run the sample code, make sure that the OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET environment variables are configured.
EnvironmentVariableCredentialsProvider credentialsProvider = CredentialsProviderFactory.newEnvironmentVariableCredentialsProvider();
// Specify the name of the bucket. Example: examplebucket.
String bucketName = "examplebucket";
// Specify the name of the output video.
String targetKey = "dest.avi";
// Specify the name of the source video.
String sourceKey = "src.mp4";
// Create an OSSClient instance.
ClientBuilderConfiguration clientBuilderConfiguration = new ClientBuilderConfiguration();
clientBuilderConfiguration.setSignatureVersion(SignVersion.V4);
OSS ossClient = OSSClientBuilder.create()
.endpoint(endpoint)
.credentialsProvider(credentialsProvider)
.clientConfiguration(clientBuilderConfiguration)
.region(region)
.build();
try {
// Create a style variable of the string type to store video transcoding parameters.
String style = String.format("video/convert,f_avi,vcodec_h265,s_1920x1080,vb_2000000,fps_30,acodec_aac,ab_100000,sn_1");
// Create an asynchronous processing instruction.
String bucketEncoded = Base64.getUrlEncoder().withoutPadding().encodeToString(bucketName.getBytes());
String targetEncoded = Base64.getUrlEncoder().withoutPadding().encodeToString(targetKey.getBytes());
String process = String.format("%s|sys/saveas,b_%s,o_%s", style, bucketEncoded, targetEncoded);
// Create an AsyncProcessObjectRequest object.
AsyncProcessObjectRequest request = new AsyncProcessObjectRequest(bucketName, sourceKey, process);
// Execute the asynchronous processing tasks.
AsyncProcessObjectResult response = ossClient.asyncProcessObject(request);
System.out.println("EventId: " + response.getEventId());
System.out.println("RequestId: " + response.getRequestId());
System.out.println("TaskId: " + response.getTaskId());
} finally {
// Shut down the OSSClient instance.
ossClient.shutdown();
}
}
}Python
If you want to use OSS SDK for Python, make sure that the SDK version is V2.18.4 or later.
# -*- coding: utf-8 -*-
import base64
import oss2
from oss2.credentials import EnvironmentVariableCredentialsProvider
def main():
# Specify the endpoint of the region in which the bucket is located. For example, if the bucket is located in the China (Hangzhou) region, set the endpoint to https://oss-cn-hangzhou.aliyuncs.com.
endpoint = 'https://oss-cn-hangzhou.aliyuncs.com'
# Obtain access credentials from environment variables. Before you run the sample code, make sure that the OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET environment variables are configured.
auth = oss2.ProviderAuthV4(EnvironmentVariableCredentialsProvider())
# Specify the name of the bucket.
bucket_name = 'examplebucket'
# Specify the ID of the Alibaba Cloud region in which the bucket is located. Example: cn-hangzhou.
region = 'cn-hangzhou'
# Create a bucket.
bucket = oss2.Bucket(auth, endpoint, bucket_name, region=region)
# Specify the name of the source video.
source_key = 'src.mp4'
# Specify the name of the output video.
target_key = 'dest.avi'
# Create a style variable of the string type to store video transcoding parameters.
style = 'video/convert,f_avi,vcodec_h265,s_1920x1080,vb_2000000,fps_30,acodec_aac,ab_100000,sn_1'
process = "{0}|sys/saveas,o_{1}".format(style,
oss2.compat.to_string(base64.urlsafe_b64encode(
oss2.compat.to_bytes(target_key))).replace('=', ''))
# Call the media processing operation.
try:
# Run the asynchronous processing task.
result = bucket.async_process_object(source_key, process)
print(f"EventId: {result.event_id}")
print(f"RequestId: {result.request_id}")
print(f"TaskId: {result.task_id}")
except Exception as e:
print(f"Error: {e}")
if __name__ == "__main__":
main()
Go
If you want to use OSS SDK for Go, make sure that the SDK version is V3.0.2 or later.
package main
import (
"encoding/base64"
"fmt"
"os"
"strings"
"github.com/aliyun/aliyun-oss-go-sdk/oss"
)
func main() {
// Obtain access credentials from environment variables. Before you run the sample code, make sure that the OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET environment variables are configured.
provider, err := oss.NewEnvironmentVariableCredentialsProvider()
if err != nil {
fmt.Println("Error:", err)
os.Exit(-1)
}
// Create an OSSClient instance.
// Specify the endpoint of the region in which the bucket is located. For example, if the bucket is located in the China (Hangzhou) region, set the endpoint to https://oss-cn-hangzhou.aliyuncs.com. Specify your actual endpoint.
client, err := oss.New("https://oss-cn-hangzhou.aliyuncs.com", "", "", oss.SetCredentialsProvider(&provider), oss.AuthVersion(oss.AuthV4), oss.Region("cn-hangzhou"))
if err != nil {
fmt.Println("Error:", err)
os.Exit(-1)
}
// Specify the name of the bucket in which the source video is stored. Example: examplebucket.
bucketName := "examplebucket"
bucket, err := client.Bucket(bucketName)
// Specify the name of the output video.
targetObject := "dest.avi"
if err != nil {
fmt.Println("Error:", err)
os.Exit(-1)
}
// Specify the name of the source video.
sourceObject := "src.mp4"
// Create a style variable of the string type to store video transcoding parameters.
style := "video/convert,f_avi,vcodec_h265,s_1920x1080,vb_2000000,fps_30,acodec_aac,ab_100000,sn_1"
process := fmt.Sprintf("%s|sys/saveas,b_%v,o_%v", style, strings.TrimRight(base64.URLEncoding.EncodeToString([]byte(bucketName)), "="), strings.TrimRight(base64.URLEncoding.EncodeToString([]byte(targetObject)), "="))
fmt.Printf("%#v\n", process)
rs, err := bucket.AsyncProcessObject(sourceObject, process)
if err != nil {
fmt.Println("Error:", err)
os.Exit(-1)
}
fmt.Printf("EventId:%s\n", rs.EventId)
fmt.Printf("RequestId:%s\n", rs.RequestId)
fmt.Printf("TaskId:%s\n", rs.TaskId)
}
FAQ
How do I fix a ResourceNotFound error for a video transcoding task?
To fix the "ResourceNotFound: The specified resource Attachment is not found" error during video transcoding, make sure that a storage bucket is created and bound to your project. For more information, see Step 2: Bind an OSS bucket.
Can I save the output object of a video transcoding task to the path of the source object?
No, you cannot save the output object of a video transcoding task to the same path as the source object. To prevent issues such as execution loops of triggers or accidental overwriting of the source object, make sure that the output path is distinct and does not use the input path as a prefix. Always specify a separate destination for transcoded objects.
Can I specify an audio bit depth in a video transcoding task?
Yes, you can specify an audio bit depth in a video transcoding task by including the pixfmt parameter in x-oss-process.
How do I retrieve the task execution result for video transcoding by using the returned task ID?
To retrieve the task execution result for video transcoding by using the returned task ID, we recommend that you call the GetTask operation in IMM.
How does OSS handle the retrieval and deletion of objects with a specific format based on their suffix during video transcoding?
OSS does not support searching for objects by suffix, as it offers an unordered storage service.
What do I do if message pushing for video transcoding is configured but the backend does not receive messages?
To troubleshoot this issue, perform the following steps:
Verify that the SMQ topic and subscription have been created.
If the subscription is missing or canceled, reconfigure it.
Restart the transcoding process based on the current subscription configuration.
Can I use a specific template to transcode a video after uploading it to OSS?
Yes, you can configure a trigger to achieve this purpose. For both existing and new videos in a bucket, video processing tasks can be initiated manually or automatically through batch processing configurations and triggers. You can apply either built-in or custom styles when creating tasks, batch processors, or triggers. For more information, see Batch processing and Triggers.
Are storage fees applied to both the transcoded video and the source video? If the transcoded video has a different prefix from the source video, will it replace the source video?
The transcoded video consumes storage space, resulting in associated charges. Using the same path for both the transcoded video and the source video may lead to looping issues.