FFMPEG挂起整个nodejs进程 [英] FFMPEG hangs the whole nodejs process
问题描述
我想要做的是使用ffmpeg制作视频的缩略图。视频数据在HTTP请求中接收，然后管道传输到ffmpeg。问题是，一旦ffmpeg子进程退出，我根本无法发回响应。
What I am trying to do is to make a thumbnail of a video using ffmpeg. The video data is received in a HTTP request and then piped to ffmpeg. The problem is that once the ffmpeg child process exits I simply can't send the response back.
这是代码：
var http = require('http'),
sys = require('sys'),
child = require('child_process')
http.createServer(function (req, res) {
im = child.spawn('ffmpeg',['-i','-','-vcodec','mjpeg','-ss','00:00:03','-vframes','1','-s','100x80','./thumb/thumbnail.jpg']);
im.on('exit', function (code, signal) {
res.writeHead(200, {'Content-Type': 'text/plain'});
res.end('{"success":true}\n');
});
req.connection.pipe(im.stdin);
}).listen(5678, "127.0.0.1");
问题是打电话：
res.writeHead(200, {'Content-Type': 'text/plain'});
res.end('{"success":true}\n');
什么也不做，客户端从未收到回应。
does nothing, the client never receives the response.
推荐答案
经过两天的调试和谷歌搜索似乎我已经发现了问题。
node.js中有两个相关的开放错误：
After two days of debugging and googling It seems like I have found the problem. There are two related open bugs in node.js responsible:
- https://github.com/joyent/node/issues/777
- https://github.com/joyent/node/issues/782
我将尝试用管道方法来描述我认为的问题：
I will try to describe what I think the problem is with the 'pipe' method:
请求流无法在ffmpeg.stdin（可能是错误＃777）上调用结尾，这会导致管道错误，但是node.js不会因为错误＃782而处理错误，同时请求流保持暂停 - 这将阻止任何响应发送。
The request stream fails to invoke end on ffmpeg.stdin (probably bug #777), this causes a broken pipe error, but node.js doesn't handle the error because of bug #782, meanwhile the request stream remains paused - this blocks any response from being sent.
黑客/解决方法是在ffmpeg退出后恢复请求流。
The hack/workaround is to resume the request stream once ffmpeg exits.
这是固定代码示例：
var http = require('http'),
sys = require('sys'),
child = require('child_process')
http.createServer(function (req, res) {
im = child.spawn('ffmpeg',['-i','-','-vcodec','mjpeg','-ss','00:00:03','-vframes','1','-s','100x80','./thumb/thumbnail.jpg']);
im.on('exit', function (code, signal) {
req.resume();
res.writeHead(200, {'Content-Type': 'text/plain'});
res.end('{"success":true}\n');
});
req.connection.pipe(im.stdin);
}).listen(5678, "127.0.0.1");
请记住，这是一个黑客/解决方法，可能会导致未来的问题node.js发布一旦他们做了关于这些错误的一些
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