我目前正在为我参与的一个项目测试几个解压库，以动态解压http文件流。我试过两个非常有前途的库，发现它们都出现了一个问题。
这就是我正在做的：
- video.avi在HTTP服务器test.com/video.zip上压缩为video.zip（约20MB）
- 从服务器读取流的HttpWebRequest
- 将HttpWebRequest ResponseStream数据写入MemoryStream
- 让解压缩库从MemoryStream中读取
- 在HttpWebRequest下载解压缩文件流时读取该流
整个想法很好，我可以解压缩压缩视频并将其直接流式传输到VLC stdin中，它的渲染也很好。然而，我必须在解压缩库上使用一个字节的读取缓冲区。任何大于一个字节的缓冲区都会导致未压缩的数据流被切断。为了进行测试，我将解压缩后的数据流写入了一个文件，并将其与原始视频进行了比较。avi和一些数据只是被解压缩跳过了。当将这些破碎的数据流式传输到VLC时，会导致大量视频伪影，播放速度也会大大降低。
如果我知道可以读取的内容的大小，我可以相应地调整缓冲区，但没有库会公开这些信息，所以我所能做的就是用一个字节的缓冲区读取数据。也许我的方法不对？或者我可能忽略了什么？
下面是一个示例代码（需要VLC）：
ICSharpCode.SharpZLib(http://icsharpcode.github.io/SharpZipLib/)
static void Main(string[] args)
{
// Initialise VLC
Process vlc = new Process()
{
StartInfo =
{
FileName = @"C:Program FilesVideoLANvlc.exe", // Adjust as required to test the code
RedirectStandardInput = true,
UseShellExecute = false,
Arguments = "-"
}
};
vlc.Start();
Stream outStream = vlc.StandardInput.BaseStream;
// Get source stream
HttpWebRequest stream = (HttpWebRequest)WebRequest.Create("http://codefreak.net/~daniel/apps/stream60s-large.zip");
Stream compressedVideoStream = stream.GetResponse().GetResponseStream();
// Create local decompression loop
MemoryStream compressedLoopback = new MemoryStream();
ZipInputStream zipStream = new ZipInputStream(compressedLoopback);
ZipEntry currentEntry = null;
byte[] videoStreamBuffer = new byte[8129]; // 8kb read buffer
int read = 0;
long totalRead = 0;
while ((read = compressedVideoStream.Read(videoStreamBuffer, 0, videoStreamBuffer.Length)) > 0)
{
// Write compressed video stream into compressed loopback without affecting current read position
long previousPosition = compressedLoopback.Position; // Store current read position
compressedLoopback.Position = totalRead; // Jump to last write position
totalRead += read; // Increase last write position by current read size
compressedLoopback.Write(videoStreamBuffer, 0, read); // Write data into loopback
compressedLoopback.Position = previousPosition; // Restore reading position
// If not already, move to first entry
if (currentEntry == null)
currentEntry = zipStream.GetNextEntry();
byte[] outputBuffer = new byte[1]; // Decompression read buffer, this is the bad one!
int zipRead = 0;
while ((zipRead = zipStream.Read(outputBuffer, 0, outputBuffer.Length)) > 0)
outStream.Write(outputBuffer, 0, outputBuffer.Length); // Write directly to VLC stdin
}
}
锐化压缩(https://github.com/adamhathcock/sharpcompress)
static void Main(string[] args)
{
// Initialise VLC
Process vlc = new Process()
{
StartInfo =
{
FileName = @"C:Program FilesVideoLANvlc.exe", // Adjust as required to test the code
RedirectStandardInput = true,
UseShellExecute = false,
Arguments = "-"
}
};
vlc.Start();
Stream outStream = vlc.StandardInput.BaseStream;
// Get source stream
HttpWebRequest stream = (HttpWebRequest)WebRequest.Create("http://codefreak.net/~daniel/apps/stream60s-large.zip");
Stream compressedVideoStream = stream.GetResponse().GetResponseStream();
// Create local decompression loop
MemoryStream compressedLoopback = new MemoryStream();
ZipReader zipStream = null;
EntryStream currentEntry = null;
byte[] videoStreamBuffer = new byte[8129]; // 8kb read buffer
int read = 0;
long totalRead = 0;
while ((read = compressedVideoStream.Read(videoStreamBuffer, 0, videoStreamBuffer.Length)) > 0)
{
// Write compressed video stream into compressed loopback without affecting current read position
long previousPosition = compressedLoopback.Position; // Store current read position
compressedLoopback.Position = totalRead; // Jump to last write position
totalRead += read; // Increase last write position by current read size
compressedLoopback.Write(videoStreamBuffer, 0, read); // Write data into loopback
compressedLoopback.Position = previousPosition; // Restore reading position
// Open stream after writing to it because otherwise it will not be able to identify the compression type
if (zipStream == null)
zipStream = (ZipReader)ReaderFactory.Open(compressedLoopback); // Cast to ZipReader, as we know the type
// If not already, move to first entry
if (currentEntry == null)
{
zipStream.MoveToNextEntry();
currentEntry = zipStream.OpenEntryStream();
}
byte[] outputBuffer = new byte[1]; // Decompression read buffer, this is the bad one!
int zipRead = 0;
while ((zipRead = currentEntry.Read(outputBuffer, 0, outputBuffer.Length)) > 0)
outStream.Write(outputBuffer, 0, outputBuffer.Length); // Write directly to VLC stdin
}
}
为了测试这段代码，我建议将SharpZipLib的输出缓冲区设置为2字节，将SharpCompress的输出缓冲区时设置为8字节。你会看到伪影，而且视频的播放速度是错误的，搜索时间应该始终与视频中计数的数字对齐。
我还没有找到任何好的解释来解释为什么从解压库中读取的更大的outputBuffer会导致这些问题，也没有找到除了拥有尽可能小的缓冲区之外的解决方法。
所以我的问题是我做错了什么，或者这是否是从流中读取压缩文件时的一般问题？如何在读取正确数据的同时增加outputBuffer？
非常感谢您的帮助！
谨致问候，Gachl
您只需要写入读取的字节数。写入整个缓冲区大小将添加额外的字节（无论以前缓冲区中发生了什么）。zipStream.Read不需要读取您请求的那么多字节。
while ((zipRead = zipStream.Read(outputBuffer, 0, outputBuffer.Length)) > 0)
outStream.Write(outputBuffer, 0, zipRead); // Write directly to VLC stdin