使用 FFMpeg 从 MemoryStream 播放视频 [英] Play a Video from MemoryStream, Using FFMpeg

问题描述

我在搜索如何使用 FFMpeg 从 TMemoryStream(或内存中的类似缓冲区)播放视频文件时遇到了困难.我见过很多东西，包括 UltraStarDX、Delphi 昂贵的 FFMpeg 组件等等.

I'm having a hard time, searching how to play a video file from a TMemoryStream (or a similar buffer in memory) using FFMpeg. I've seen many things, including UltraStarDX, expensive FFMpeg components for Delphi and so on.

一个名为 FFMpeg Vcl Player 的组件声称可以播放来自一个内存流.我下载了试用版，我猜它使用了 CircularBuffer.pas(也许).

One component called FFMpeg Vcl Player claims to play video formats from a memory stream. I downloaded the trial version and I guess it uses CircularBuffer.pas for that matter (maybe).

有人知道怎么做吗?

现在更好的问题是如何使用 FFMpeg 或类似库播放加密的视频文件.

Now the better question is how to play an encrypted video file, using FFMpeg or similar libraries.

推荐答案

要从内存流播放视频，您可以使用自定义AVIOContext.

To play video from memory stream, you can use custom AVIOContext.

static const int kBufferSize = 4 * 1024;

class my_iocontext_private
{
private:
    my_iocontext_private(my_iocontext_private const &);
    my_iocontext_private& operator = (my_iocontext_private const &);

public:
    my_iocontext_private(IInputStreamPtr inputStream)
       : inputStream_(inputStream)
       , buffer_size_(kBufferSize)
       , buffer_(static_cast<unsigned char*>(::av_malloc(buffer_size_))) {
    ctx_ = ::avio_alloc_context(buffer_, buffer_size_, 0, this,
           &my_iocontext_private::read, NULL, &my_iocontext_private::seek); 
    }

    ~my_iocontext_private() { 
        ::av_free(ctx_);
        ::av_free(buffer_); 
    }

    void reset_inner_context() { ctx_ = NULL; buffer_ = NULL; }

    static int read(void *opaque, unsigned char *buf, int buf_size) {
        my_iocontext_private* h = static_cast<my_iocontext_private*>(opaque);
        return h->inputStream_->Read(buf, buf_size); 
    }

    static int64_t seek(void *opaque, int64_t offset, int whence) {
        my_iocontext_private* h = static_cast<my_iocontext_private*>(opaque);

        if (0x10000 == whence)
            return h->inputStream_->Size();

        return h->inputStream_->Seek(offset, whence); 
    }

    ::AVIOContext *get_avio() { return ctx_; }

    private:
       IInputStreamPtr inputStream_; // abstract stream interface, You can adapt it to TMemoryStream  
       int buffer_size_;
       unsigned char * buffer_;  
       ::AVIOContext * ctx_;
   };


   //// ..........

   /// prepare input stream:
   IInputStreamPtr inputStream = MyCustomCreateInputStreamFromMemory();

   my_iocontext_private priv_ctx(inputStream);
   AVFormatContext * ctx = ::avformat_alloc_context();
   ctx->pb = priv_ctx.get_avio();

   int err = avformat_open_input(&ctx, "arbitrarytext", NULL, NULL);
   if (err < 0) 
       return -1;

   //// normal usage of ctx
   //// avformat_find_stream_info(ctx, NULL);
   //// av_read_frame(ctx, &pkt); 
   //// etc..

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