Flutter视频编码配置插件h264_profile_level_id的使用

发布于 1周前 作者 yibo5220 来自 Flutter

Flutter视频编码配置插件h264_profile_level_id的使用

h264_profile_level_id 是一个用于处理H.264 profile-level-id 值的Dart工具,基于Google的libwebrtc C++代码。它提供了多种功能来解析、生成和比较H.264的Profile和Level信息。下面我们将详细介绍如何使用这个插件,并提供一个完整的示例demo。

1. API介绍

h264_profile_level_id 提供了以下API:

  • H264 Profile标识符

    • ProfileConstrainedBaseline
    • ProfileBaseline
    • ProfileMain
    • ProfileConstrainedHigh
    • ProfileHigh
  • H264 Level标识符

    • Level1_b, Level1, Level1_1, Level1_2, Level1_3
    • Level2, Level2_1, Level2_2
    • Level3, Level3_1, Level3_2
    • Level4, Level4_1, Level4_2
    • Level5, Level5_1, Level5_2
  • 函数

    • parseProfileLevelId(str):解析表示为3个十六进制字节字符串的profile-level-id
    • profileLevelIdToString(profile_level_id):返回profile-level-id的规范字符串表示(3个十六进制字节),或对于无效的profile-level-id返回null。
    • parseSdpProfileLevelId(params):解析SDP键值对中表示为3个十六进制字节字符串的profile-level-id
    • isSameProfile(params1, params2):检查两个参数对象是否具有相同的H.264 Profile。
    • generateProfileLevelIdForAnswer(local_supported_params, remote_offered_params):根据本地支持的参数和远程提供的参数生成适合SDP协商的profile-level-id
    • ProfileLevelId:包含H.264的Profile和Level信息。

2. 示例代码

下面是一个完整的示例demo,展示了如何使用h264_profile_level_id插件来处理H.264的profile-level-id

import 'package:h264_profile_level_id/h264_profile_level_id.dart';

void main() {
  // 创建一个ProfileLevelId实例
  final ProfileLevelId profileLevelId = ProfileLevelId(
    profile: H264Utils.ProfileMain,  // 设置Profile为Main
    level: H264Utils.Level3_1,      // 设置Level为3.1
  );

  // 打印Profile和Level
  print('profile: ${profileLevelId.profile}, level: ${profileLevelId.level}');
  // 输出: profile: 3, level: 31

  // 将ProfileLevelId转换为字符串
  String? profileLevelIdString = H264Utils.profileLevelIdToString(profileLevelId);
  print('profile-level-id string: $profileLevelIdString');
  // 输出: profile-level-id string: 4d0301

  // 解析字符串为ProfileLevelId
  String inputStr = '4d0301';  // Main Profile, Level 3.1
  ProfileLevelId? parsedProfileLevelId = H264Utils.parseProfileLevelId(inputStr);
  if (parsedProfileLevelId != null) {
    print('Parsed profile: ${parsedProfileLevelId.profile}, level: ${parsedProfileLevelId.level}');
    // 输出: Parsed profile: 3, level: 31
  } else {
    print('Invalid profile-level-id string');
  }

  // 检查两个Codec参数对象是否具有相同的Profile
  Map<String, dynamic> params1 = {'profile-level-id': '4d0301'};
  Map<String, dynamic> params2 = {'profile-level-id': '4d0301'};
  bool isSame = H264Utils.isSameProfile(params1, params2);
  print('Is same profile: $isSame');
  // 输出: Is same profile: true

  // 生成适合SDP协商的profile-level-id
  Map<String, dynamic> localSupportedParams = {'profile-level-id': '4d0301'};
  Map<String, dynamic> remoteOfferedParams = {'profile-level-id': '4d0301'};
  String? generatedProfileLevelId = H264Utils.generateProfileLevelIdForAnswer(localSupportedParams, remoteOfferedParams);
  print('Generated profile-level-id for SDP answer: $generatedProfileLevelId');
  // 输出: Generated profile-level-id for SDP answer: 4d0301
}

更多关于Flutter视频编码配置插件h264_profile_level_id的使用的实战系列教程也可以访问 https://www.itying.com/category-92-b0.html

1 回复

更多关于Flutter视频编码配置插件h264_profile_level_id的使用的实战系列教程也可以访问 https://www.itying.com/category-92-b0.html


在Flutter中,如果你需要配置视频编码参数,特别是H.264编码的profile_level_id,通常会涉及到调用原生平台(iOS和Android)的编码库。Flutter本身不提供直接的视频编码功能,但你可以通过插件来访问这些功能。

以下是一个基本的示例,展示如何通过Flutter插件来配置H.264编码的profile_level_id。这里我们假设你已经有一个可以访问原生视频编码功能的Flutter插件。

1. 创建Flutter插件

首先,你需要创建一个Flutter插件来封装原生平台的功能。这里假设你已经有一个Flutter插件项目。

iOS部分

ios/Classes目录下创建一个Objective-C或Swift文件,例如VideoEncoder.swift,用于配置和执行视频编码。

// VideoEncoder.swift
import Foundation
import AVFoundation

@objc class VideoEncoder: NSObject {
    
    @objc static func encodeVideo(withFilePath inputPath: String, outputPath: String, profileLevelId: String, completion: @escaping (Bool, Error?) -> Void) {
        guard let inputURL = URL(fileURLWithPath: inputPath),
              let outputURL = URL(fileURLWithPath: outputPath) else {
            completion(false, NSError(domain: "", code: -1, userInfo: [NSLocalizedDescriptionKey: "Invalid URL"]))
            return
        }
        
        let asset = AVAsset(url: inputURL)
        guard let track = asset.tracks(withMediaType: .video).first else {
            completion(false, NSError(domain: "", code: -1, userInfo: [NSLocalizedDescriptionKey: "No video track found"]))
            return
        }
        
        let videoComposition = AVMutableVideoComposition()
        videoComposition.frameDuration = CMTimeMake(1, 30)
        videoComposition.renderSize = track.naturalSize
        
        let instruction = AVMutableVideoCompositionInstruction()
        instruction.timeRange = CMTimeRangeMake(kCMTimeZero, asset.duration)
        
        let layerInstruction = AVMutableVideoCompositionLayerInstruction(assetTrack: track)
        instruction.layerInstructions = [layerInstruction] as [AVVideoCompositionLayerInstruction]
        videoComposition.instructions = [instruction] as [AVVideoCompositionInstruction]
        
        let exporter = AVAssetExportSession(asset: asset, presetName: AVAssetExportPresetHighestQuality)
        exporter.outputFileType = AVFileType.mp4
        exporter.outputURL = outputURL
        exporter.videoComposition = videoComposition
        
        // Configure the video settings with profileLevelId
        var videoSettings: [AVVideoCompressionPropertiesKey : Any] = [:]
        videoSettings[AVVideoCodecKey] = AVVideoCodecType.h264
        videoSettings[AVVideoCompressionPropertiesKey.profileLevel] = profileLevelId
        videoSettings[AVVideoWidthKey] = track.naturalSize.width
        videoSettings[AVVideoHeightKey] = track.naturalSize.height
        videoSettings[AVVideoAverageBitRateKey] = 5000000  // Example bitrate
        
        exporter.videoSettings = videoSettings
        
        exporter.exportAsynchronously(completionHandler: {
            switch exporter.status {
            case .completed:
                completion(true, nil)
            case .failed:
                completion(false, exporter.error)
            case .cancelled, .exporting, .waiting, .unknown:
                completion(false, NSError(domain: "", code: -1, userInfo: [NSLocalizedDescriptionKey: "Export session status not completed"]))
            }
        })
    }
}

Android部分

android/src/main/java/com/yourpackage/videoencoder目录下创建一个Java或Kotlin文件,例如VideoEncoder.java,用于配置和执行视频编码。

// VideoEncoder.java
package com.yourpackage.videoencoder;

import android.media.MediaCodec;
import android.media.MediaFormat;
import android.util.Log;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;

public class VideoEncoder {

    private static final String TAG = "VideoEncoder";

    public static void encodeVideo(String inputPath, String outputPath, String profileLevelId, Callback callback) {
        // Note: This is a simplified example. In a real-world scenario, you'd need to set up
        // a MediaExtractor to read the input file, a MediaCodec to encode it, and a MediaMuxer to
        // write the encoded data to the output file.

        // For the sake of this example, we're just logging the parameters.
        Log.i(TAG, "Input Path: " + inputPath);
        Log.i(TAG, "Output Path: " + outputPath);
        Log.i(TAG, "Profile Level ID: " + profileLevelId);

        // Here you would set up the MediaCodec with the specified profileLevelId
        // and perform the encoding process.

        // For demonstration purposes, we'll just call the callback with a success result.
        callback.onEncodingComplete(true, null);
    }

    public interface Callback {
        void onEncodingComplete(boolean success, Exception e);
    }
}

2. 在Flutter中调用插件

在Flutter项目的lib目录下创建一个Dart文件,例如video_encoder.dart,用于封装对原生插件的调用。

import 'dart:async';
import 'dart:typed_data';
import 'package:flutter/services.dart';

class VideoEncoder {
  static const MethodChannel _channel = MethodChannel('com.yourpackage/video_encoder');

  static Future<void> encodeVideo(String inputPath, String outputPath, String profileLevelId) async {
    try {
      await _channel.invokeMethod('encodeVideo', {
        'inputPath': inputPath,
        'outputPath': outputPath,
        'profileLevelId': profileLevelId,
      });
    } on PlatformException catch (e) {
      throw FormatException(e.message ?? "Unknown error");
    }
  }
}

3. 配置原生方法通道

在插件的iOS和Android项目中配置方法通道,以便Flutter可以调用原生方法。

iOS

ios/Classes/YourPlugin.m中:

#import <Flutter/Flutter.h>
#import "VideoEncoder.h"

@interface YourPlugin : NSObject<FlutterPlugin>
@end

@implementation YourPlugin
+ (void)registerWithRegistrar:(NSObject<FlutterPluginRegistrar>*)registrar {
    FlutterMethodChannel* channel = [FlutterMethodChannel
        methodChannelWithName:@"com.yourpackage/video_encoder"
                    binaryMessenger:registrar.messenger];
    
    [YourPluginInstance sharedInstance] setupWithChannel:channel];
}

@end

@interface YourPluginInstance : NSObject
+ (instancetype)sharedInstance;
- (void)setupWithChannel:(FlutterMethodChannel*)channel;
@end

@implementation YourPluginInstance
+ (instancetype)sharedInstance {
    static YourPluginInstance *instance;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        instance = [[self alloc] init];
    });
    return instance;
}

- (void)setupWithChannel:(FlutterMethodChannel*)channel {
    [channel setMethodCallHandler:^(FlutterMethodCall* call, FlutterResult result) {
        if ([call.method isEqualToString:@"encodeVideo"]) {
            NSDictionary *arguments = call.arguments;
            NSString *inputPath = arguments[@"inputPath"];
            NSString *outputPath = arguments[@"outputPath"];
            NSString *profileLevelId = arguments[@"profileLevelId"];
            
            [VideoEncoder encodeVideoWithFilePath:inputPath
                                       outputPath:outputPath
                                  profileLevelId:profileLevelId
                                     completion:^(BOOL success, NSError *error) {
                                       if (success) {
                                           result(success);
                                       } else {
                                           result(FlutterError(code: @"ERROR", message: error.localizedDescription, details: nil));
                                       }
                                     }];
        } else {
            result(FlutterMethodNotImplemented);
        }
    }];
}
@end

Android

android/src/main/kotlin/com/yourpackage/yourplugin/YourPlugin.kt中:

package com.yourpackage.yourplugin

import android.content.Context
import androidx.annotation.NonNull
import io.flutter.embedding.engine.plugins.FlutterPlugin
import io.flutter.embedding.engine.plugins.activity.ActivityAware
import io.flutter
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