FrameGrab Can't detect format of MP4 after being resized with ffmpeg

I’m creating a program that opens an MP4 file and returns the next frame as a BufferedImage upon request (Pretty much viewing an MP4 frame by frame).

My code is working fine on my original test MP4 but if I resize that MP4 using ffmpeg i get a

org.jcodec.api.UnsupportedFormatException: Could not detect the format of the input video.
	at org.jcodec.api.FrameGrab.createFrameGrab(FrameGrab.java:55)

Resize Command:

ffmpeg -i input.mp4 -s 1280x720 output.mp4

Code:

final FileChannelWrapper wrapper = NIOUtils.readableChannel(_FILE_);
final FrameGrab grab = FrameGrab.createFrameGrab(wrapper);

I’m pretty new to jcodec and media encoding/decoding in general so I’m not sure if this is a problem with my resize command, my code, or the library.

[svitvitskiy]

I am not sure, doesn’t happen on my machine.

As an alternative, try importing all jcodec, jcodec-javase, jcodec-samples into your Eclipse or IntelliJ as maven projects. Then simply run the class FrameGrabDemo.

[TheStonedTurtle]

Running mvn clean install on my clone of the repo is giving me the below test failure.

Running org.jcodec.movtool.MetadataEditorTest
[INFO]	. (:0):	Relocating movie header to the end of the file.
[INFO]	. (:0):	Relocating movie header to the end of the file.
Tests run: 5, Failures: 0, Errors: 1, Skipped: 0, Time elapsed: 0.133 sec <<< FAILURE!
testKeyedWriteSlow(org.jcodec.movtool.MetadataEditorTest)  Time elapsed: 0.044 sec  <<< ERROR!
java.lang.NullPointerException
	at org.jcodec.movtool.MetadataEditorTest.keyedWriteSub(MetadataEditorTest.java:82)
	at org.jcodec.movtool.MetadataEditorTest.testKeyedWriteSlow(MetadataEditorTest.java:56)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:566)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
	at org.apache.maven.surefire.junit4.JUnit4Provider.execute(JUnit4Provider.java:252)
	at org.apache.maven.surefire.junit4.JUnit4Provider.executeTestSet(JUnit4Provider.java:141)
	at org.apache.maven.surefire.junit4.JUnit4Provider.invoke(JUnit4Provider.java:112)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:566)
	at org.apache.maven.surefire.util.ReflectionUtils.invokeMethodWithArray(ReflectionUtils.java:189)
	at org.apache.maven.surefire.booter.ProviderFactory$ProviderProxy.invoke(ProviderFactory.java:165)
	at org.apache.maven.surefire.booter.ProviderFactory.invokeProvider(ProviderFactory.java:85)
	at org.apache.maven.surefire.booter.ForkedBooter.runSuitesInProcess(ForkedBooter.java:115)
	at org.apache.maven.surefire.booter.ForkedBooter.main(ForkedBooter.java:75)