AVAssetWriter追加HDR元数据报错-12743，求排查元数据拷贝问题

云上老周

2026-7-8

解决方案

报错-12743对应AVAssetWriterErrorCodeInvalidPixelBufferAttributes，核心问题是kCVImageBufferAmbientViewingEnvironmentKey的附加数据格式不符合要求。

禁止直接转成NSData/CFData：该key要求的附加值必须是符合特定结构的CFDictionary，而非序列化后的plist二进制数据。你从CMFormatDescription.Extensions.Value获取的propertyListRepresentation是序列化后的结果，这不符合AVAssetWriter的格式要求。
正确提取与附加方式：直接将环境数据转换为CFDictionary后附加，跳过序列化步骤：

if let ambientEnv = sampleBuffer.formatDescription?.extensions[.ambientViewingEnvironment] as? CFDictionary {
    CVBufferSetAttachment(dstPixelBuffer, kCVImageBufferAmbientViewingEnvironmentKey, ambientEnv, .shouldPropagate)
}

拷贝附件的修正逻辑：如果直接拷贝源缓冲区的附件，需先判断附件类型：
1. 若源附件是序列化后的CFData，需先反序列化为CFDictionary再附加
2. 若源附件本身就是CFDictionary，可直接附加

var attachmentMode: CVAttachmentMode = .shouldPropagate
if let attachment = CVBufferCopyAttachment(sourcePixelBuffer!, kCVImageBufferAmbientViewingEnvironmentKey, &attachmentMode) {
    if let data = attachment as? CFData,
       let ambientDict = try? PropertyListSerialization.propertyList(from: data as Data, options: [], format: nil) as? CFDictionary {
        CVBufferSetAttachment(dstPixelBuffer, kCVImageBufferAmbientViewingEnvironmentKey, ambientDict, attachmentMode)
    } else if let ambientDict = attachment as? CFDictionary {
        CVBufferSetAttachment(dstPixelBuffer, kCVImageBufferAmbientViewingEnvironmentKey, ambientDict, attachmentMode)
    }
}

AVAssetWriter对HDR元数据的格式要求严格，必须传递原始字典结构，这是解决报错的关键。