Question

我正在尝试使用以下代码访问ALAssets库中的视频数据

        ALAssetRepresentation *rep = [asset defaultRepresentation];
        Byte *buffer = (Byte*)malloc(rep.size);
        NSError *error = nil;
        NSUInteger buffered = [rep getBytes:buffer fromOffset:0.0 length:rep.size error:&error];
        NSData *data = [NSData dataWithBytesNoCopy:buffer length:buffered freeWhenDone:YES];

它适用于小型视频和图片，但如果我想要获取大型视频，代码会崩溃说

*由于未捕获的异常'NSInvalidArgumentException'而终止应用程序，原因：'* - [NSConcreteData initWithBytes：length：copy：freeWhenDone：bytesAreVM：]：absurd length：4294967295，最大大小：2147483648字节“

我不知道发生了什么。任何一个想法？

提前致谢！

Answer 1

我找到了解决方案。我想当我们上传大文件时崩溃可能是由于巨大的内存峰值，因为我正在缓冲数据。现在我将文件数据读取为5 MB块，这可以解决崩溃问题。我正在粘贴下面的代码。

- (NSData *)getDataPartAtOffset:(NSInteger)offset  {
__block NSData *chunkData = nil;
if (fileAsset_){
    static const NSUInteger BufferSize = PART_SIZE; // 5 MB chunk
    ALAssetRepresentation *rep = [fileAsset_ defaultRepresentation];
    uint8_t *buffer = calloc(BufferSize, sizeof(*buffer));
    NSUInteger bytesRead = 0;
    NSError *error = nil;

    @try
    {
        bytesRead = [rep getBytes:buffer fromOffset:offset length:BufferSize error:&error];
        chunkData = [NSData dataWithData:[NSData dataWithBytesNoCopy:buffer length:bytesRead freeWhenDone:NO]];
    }
    @catch (NSException *exception)
    {
        free(buffer);
        chunkData = nil;
        // Handle the exception here...
    }

    free(buffer);
} else {
    NSLog(@"failed to retrive Asset");
}
return chunkData;

}

我将把这个功能称为

   int offset = 0; // offset that keep tracks of chunk data

  do {
        @autoreleasepool {
            NSData *chunkData = [self getDataPartAtOffset:offset];;

            if (!chunkData || ![chunkData length]) { // finished reading data
                break;
            }

            // do your stuff here

            offset +=[chunkData length];
        }
    } while (1);

Answer 2

chilitechno's位here为我工作。

ALAssets获取视频数据

2 个答案: