java - 使用 ffmpeg 降低比特率

Question

我有这个命令与 ffmpeg 一起运行以降低比特率。

ffmpeg -y -i input.mp4 -b:v 1024k output_1024k.mp4

我们要在哪里获取输入文件并降低它的比特率(只有 1024k)。它在命令行中工作。
现在，我喜欢通过 Java 降低比特率。我决定使用 bytedeco/javacv FFmpegFrameGrabber 和 FFmpegFrameRecorder 来执行相同的功能。下面是我的代码:

FFmpegFrameGrabber grabber = new FFmpegFrameGrabber("input.mp4");
            grabber.start();

            FrameRecorder recorder = new FFmpegFrameRecorder("out.mp4", grabber.getAudioChannels());
            recorder.setSampleRate(256);
            recorder.start();

            Frame frame;
            while ((frame = grabber.grabFrame()) != null) {
                recorder.record(frame);
            }
            recorder.stop();
            grabber.stop(); 

但它说的是以下错误:

org.bytedeco.javacv.FrameRecorder$Exception: avcodec_open2() error -22: Could not open audio codec.
    at org.bytedeco.javacv.FFmpegFrameRecorder.startUnsafe(FFmpegFrameRecorder.java:732)
    at org.bytedeco.javacv.FFmpegFrameRecorder.start(FFmpegFrameRecorder.java:351)
    at com.goxhere.api.monte.resources.VideoResource.uploadFile(VideoResource.java:337)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.glassfish.jersey.server.model.internal.ResourceMethodInvocationHandlerFactory.lambda$static$0(ResourceMethodInvocationHandlerFactory.java:74)
    at org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher$1.run(AbstractJavaResourceMethodDispatcher.java:144)
    at org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher.invoke(AbstractJavaResourceMethodDispatcher.java:161)
    at org.glassfish.jersey.server.model.internal.JavaResourceMethodDispatcherProvider$TypeOutInvoker.doDispatch(JavaResourceMethodDispatcherProvider.java:247)
    at org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher.dispatch(AbstractJavaResourceMethodDispatcher.java:99)
    at org.glassfish.jersey.server.model.ResourceMethodInvoker.invoke(ResourceMethodInvoker.java:388)
    at org.glassfish.jersey.server.model.ResourceMethodInvoker.apply(ResourceMethodInvoker.java:346)
    at org.glassfish.jersey.server.model.ResourceMethodInvoker.apply(ResourceMethodInvoker.java:102)
    at org.glassfish.jersey.server.ServerRuntime$2.run(ServerRuntime.java:337)
    at org.glassfish.jersey.internal.Errors$1.call(Errors.java:271)
    at org.glassfish.jersey.internal.Errors$1.call(Errors.java:267)
    at org.glassfish.jersey.internal.Errors.process(Errors.java:315)
    at org.glassfish.jersey.internal.Errors.process(Errors.java:297)
    at org.glassfish.jersey.internal.Errors.process(Errors.java:267)
    at org.glassfish.jersey.process.internal.RequestScope.runInScope(RequestScope.java:280)
    at org.glassfish.jersey.server.ServerRuntime.process(ServerRuntime.java:316)
    at org.glassfish.jersey.server.ApplicationHandler.handle(ApplicationHandler.java:1084)
    at org.glassfish.jersey.servlet.WebComponent.serviceImpl(WebComponent.java:418)
    at org.glassfish.jersey.servlet.WebComponent.service(WebComponent.java:372)
    at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:389)
    at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:342)
    at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:229)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:478)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:80)
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:624)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:799)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:861)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1455)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:748)

基本上，错误表明我的音频编解码器有问题，但是当我尝试直接运行 ffmpeg 命令行时，它会很好地降低比特率。我们是否缺少 javacode 中的一些设置？谢谢你。

Answer 1

问题解决了。我们需要启用调试日志记录，这样我们才能看到出了什么问题。在这种情况下，它表示我们缺少采样率等参数。