2

我正在使用高速公路|python 运行 websocket 服务器。在服务器端，我还运行了一个 gstreamer 管道，我使用它来使用“appsink”捕获 webm 帧。实现的 gstreamer 管道是：

gst-launch-1.0 v4l2src ! video/x-raw,width=640,height=480 ! videoconvert ! vp8enc ! webmmux ! appsink name="sink"

每次，我在应用程序接收器中收到一个缓冲区，我使用 sendMessage 通过 websocket 将其作为二进制“消息”发送。

def on_new_buffer(appsink):
    global once
    gstsample = appsink.emit('pull-sample')
    gstbuffer = gstsample.get_buffer()
    frame_data = gstbuffer.extract_dup(0,gstbuffer.get_size())
    for c in global_clients:
        c.sendMessage(frame_data,True)
        print("Directly sent: {0} bytes".format(len(frame_data)))

    return False

在客户端，我收到了一个复杂的 frame_data blob 流。有一个 FileReader、MediaSource 和源缓冲区。每当接收到 frame_data 时，都会使用 filereader 将其作为缓冲区读取。如果文件读取器正忙于读取前一个 frame_data，它会将其附加到“buffer_pool”。一旦 frame_data 被读取为缓冲区，它就会被附加到“sourceBuffer”。如果“sourceBuffer”仍在更新前一个块，它将被附加到“sourceBufferpool”。

    <script>
    var video = document.getElementById('v');
    var playButton = document.getElementById('playbutton');
    var mediaSource;
    var sourceBuffer;
    var buffer_pool = [];
    var sourceBufferpool = [];

    function setupVideo() {
        window.MediaSource = window.MediaSource || window.WebKitMediaSource;
        if (!!!window.MediaSource) {
            alert('MediaSource API is not available');
        }
        mediaSource = new MediaSource();
        video.src = window.URL.createObjectURL(mediaSource);
        mediaSource.addEventListener('sourceopen', function (e) {
            try {
                sourceBuffer = mediaSource.addSourceBuffer('video/webm; codecs="vp8"');
            } catch(e) {
                console.log('Exception calling addSourceBuffer for video', e);
                return;
            }

            //sourceBuffer.addEventListener('updatestart', function(e) { console.log('updatestart: ' + e.target + mediaSource.readyState); });
            //sourceBuffer.addEventListener('updateend', function(e) { console.log('updateend: ' + e.target + mediaSource.readyState); });
            sourceBuffer.addEventListener('error', function(e) { console.log('error: ' + e.target + mediaSource.readyState); });
            sourceBuffer.addEventListener('abort', function(e) { console.log('abort: ' + e.target + mediaSource.readyState); });

            sourceBuffer.addEventListener('update', function() {
                if (sourceBufferpool.length > 0 && !sourceBuffer.updating) {
                    try {
                        sourceBuffer.appendBuffer(sourceBufferpool.shift());
                        console.log('update: pooled buffer appended ' + sourceBufferpool.length + mediaSource.readyState);
                    }catch(e){
                        console.log('Exception calling appendBuffer for video ', e);
                        return;
                    }
                }
            },false)

            if (video.paused) {
                video.play()
            }

            startWSStreaming();
        },false)

        mediaSource.addEventListener('sourceended', function(e) { console.log('sourceended: ' + mediaSource.readyState); });
        mediaSource.addEventListener('sourceclose', function(e) { console.log('sourceclose: ' + mediaSource.readyState); });
        mediaSource.addEventListener('error', function(e) { console.log('error: ' + mediaSource.readyState); });

    }

    function startWSStreaming() {
        var reader = new FileReader();

        reader.onload = function (evt) {
            if (sourceBuffer.updating || sourceBufferpool.length > 0){
                sourceBufferpool.push(new Uint8Array(evt.target.result));
                console.log('update: pooled buffer appended ' + sourceBufferpool.length + mediaSource.readyState);
            }else{
                sourceBuffer.appendBuffer(new Uint8Array(evt.target.result));
                console.log('update: direct buffer appended ' + sourceBufferpool.length + mediaSource.readyState);
            }
        }

        reader.onloadend = function (evt) {
            if (buffer_pool.length > 0) {
                var chunk = new Blob([buffer_pool.shift()], {type: 'video/webm'});
                evt.target.readAsArrayBuffer(chunk);
                console.log('Processed buffer pool: current size ' + buffer_pool.length);
            }
        }

        ws = new WebSocket("ws://localhost:9000/");
        ws.onopen = function () {
            document.getElementById("MSG1").innerHTML = 'Websocket opened <br>';
        }
        ws.onmessage = function(e) {
            myBuffer = e.data;
            if (reader.readyState == 1 || buffer_pool.length > 0) {
                buffer_pool.push(myBuffer);
                console.log('Received buffer pooled: current size ' + buffer_pool.length);
            }else{
                var chunk = new Blob([myBuffer], {type: 'video/webm'});
                reader.readAsArrayBuffer(chunk);
                console.log('First buffer processed');
            }
        }

    }       
</script>

现在，最终结果是，我在浏览器窗口中只看到一帧，然后视频冻结。检查 chrome://media-internals/ 后，我得到以下线索：

Timestamp   Property    Value
00:00:00 00 pipeline_state  kCreated
00:00:00 00 EVENT   PIPELINE_CREATED
00:00:00 00 EVENT   WEBMEDIAPLAYER_CREATED
00:00:00 00 url blob:http%3A//localhost%3A8080/09060a78-9759-4fcd-97a2-997121ba6122
00:00:00 00 pipeline_state  kInitDemuxer
00:00:01 668    duration    unknown
00:00:01 669    pipeline_state  kInitVideoRenderer
00:00:01 685    pipeline_state  kPlaying
00:00:03 820    EVENT   PLAY
00:00:04 191    error   Got a block with a timecode before the previous block.
00:00:04 191    pipeline_error  pipeline: decode error
00:00:04 191    pipeline_state  kStopping
00:00:04 192    pipeline_state  kStopped
00:00:28 483    EVENT   WEBMEDIAPLAYER_DESTROYED

呼，好长的描述！！！我希望你能做到这一点。现在，真正的问题：

  1. 为什么只播放一帧后视频就卡住了？
  2. 是因为websocket“sendMessage”方法，因为我将webm块视为不同的消息，而这应该需要作为“sendMessageFrameData”处理？
  3. 我需要对到达的 frame_data 进行一些排序，以便按照发送顺序接收它们吗？
  4. 还是我的整个方法不正确？

请帮忙！

4

0 回答 0