Play a Video from MemoryStream, Using FFMpeg

Question

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,

Answer 1

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(::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(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(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..