[Libav-user] variable scope into callback av_log_set_callback and multi threading

[Algarve Branqueira]

the attached code is better 😀

Le jeu. 24 mars 2022 à 19:53, Algarve Branqueira <branqueira at gmail.com> a
écrit :

> I never said the opposite.
> I listened to your advice, you are right. there was never any question of
> having a logging instance for each thread, but the object makes it possible
> to have a link between the threads.
>
> the logging is not based on an instance but on a static class.
>
> I have nothing to hide, I show you my code, as you can see, there is never
> any mention of an object in the code.
>
> the question is just how to call code at the end of ffmpeg's worker thread.
>
> because in the code in c to call java it is necessary.
>
> 1/ attach the c thread to the java thread
>                  *res =(*javaVM)->AttachCurrentThreadAsDaemon(javaVM,
> (void**)&jniEnv, NULL);  *
> 2/ make your code, your blah blah
>
> 3/ at the closure of the thread in c, detach the java thread
>
> *(*javaVM)->*DetachCurrentThread(*javaVM*);
>
>
>
> don't see evil everywhere, I asked a question, I heard your advice, I
> followed it
>
> Cordially
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> *#include <jni.h>#include <libavdevice/avdevice.h>#include
> <pthread.h>#define LOGGER_CLASS "fr/ms/ffmpeg/FFMPEG_LOG"#define
> THREAD_FFMPEG_WORKER "FFMPEG-Worker-%i"JavaVM *javaVM;__thread JNIEnv
> *jniEnv;jclass clazzLogger;jmethodID jMethodGetLogLevel;jmethodID
> jMethodGetLogLevelValue;jmethodID callLoggerMethod;int compteur = 0;int
> init_JNI() { if (jniEnv == NULL) { int res = (*javaVM)->GetEnv(javaVM,
> (void**)&jniEnv, JNI_VERSION_1_8); if (res == JNI_EDETACHED) {
> JavaVMAttachArgs args; args.version = JNI_VERSION_1_8; args.name
> <http://args.name> = malloc(128); sprintf(args.name <http://args.name>,
> THREAD_FFMPEG_WORKER, compteur); res
> =(*javaVM)->AttachCurrentThreadAsDaemon(javaVM, (void**)&jniEnv, NULL); if
> (res != JNI_OK) { return res; } compteur++; } } return JNI_OK;}void
> wrapper_logger(void *ptr, int level, const char* fmt, va_list vl){ if
> (init_JNI() != JNI_OK) { return; } jobject enumObjLogLevel =
> (*jniEnv)->CallStaticObjectMethod(jniEnv, clazzLogger, jMethodGetLogLevel);
> if ((*jniEnv)->ExceptionOccurred(jniEnv)) {
> (*jniEnv)->ExceptionClear(jniEnv); (*jniEnv)->DeleteLocalRef(jniEnv,
> enumObjLogLevel); return; } int av_level = (int)
> (*jniEnv)->CallIntMethod(jniEnv, enumObjLogLevel, jMethodGetLogLevelValue);
> (*jniEnv)->DeleteLocalRef(jniEnv, enumObjLogLevel); if
> ((*jniEnv)->ExceptionOccurred(jniEnv)) { (*jniEnv)->ExceptionClear(jniEnv);
> return; } if (level > av_level) return; char buffer[1024]; int res =
> vsprintf(buffer, fmt, vl); if (res < 0) return; jstring jstr =
> (*jniEnv)->NewStringUTF(jniEnv, buffer); if (jstr != NULL) {
> (*jniEnv)->CallStaticVoidMethod(jniEnv, clazzLogger, callLoggerMethod,
> level, jstr); (*jniEnv)->DeleteLocalRef(jniEnv, jstr); if
> ((*jniEnv)->ExceptionOccurred(jniEnv)) { (*jniEnv)->ExceptionClear(jniEnv);
> return; } }}int init_logger() { clazzLogger = (*jniEnv)->FindClass(jniEnv,
> LOGGER_CLASS); clazzLogger = (*jniEnv)->NewGlobalRef(jniEnv,clazzLogger);
> jMethodGetLogLevel = (*jniEnv)->GetStaticMethodID(jniEnv, clazzLogger,
> "getLogLevel", "()Lfr/ms/ffmpeg/FFMPEG_AV_LOG;"); jobject enumObjLogLevel =
> (*jniEnv)->CallStaticObjectMethod(jniEnv, clazzLogger, jMethodGetLogLevel);
> jthrowable exc = (*jniEnv)->ExceptionOccurred(jniEnv); if (exc) {
> (*jniEnv)->ExceptionClear(jniEnv); return -1; } jclass enumClass =
> (*jniEnv)->GetObjectClass(jniEnv, enumObjLogLevel); jMethodGetLogLevelValue
> = (*jniEnv)->GetMethodID(jniEnv, enumClass, "getValue", "()I"); int
> av_level = (int) (*jniEnv)->CallIntMethod(jniEnv, enumObjLogLevel,
> jMethodGetLogLevelValue); exc = (*jniEnv)->ExceptionOccurred(jniEnv); if
> (exc) { (*jniEnv)->ExceptionClear(jniEnv); return -1; } callLoggerMethod =
> (*jniEnv)->GetStaticMethodID(jniEnv, clazzLogger, "callLogger0",
> "(ILjava/lang/String;)V"); return JNI_OK;}jint JNI_OnLoad(JavaVM *vm, void
> *reserved) { javaVM = vm; if ((*vm)->GetEnv(vm, (void**)&jniEnv,
> JNI_VERSION_1_8) != JNI_OK) return -1; if (init_logger() != JNI_OK) return
> -1; av_log_set_callback(wrapper_logger); avdevice_register_all();
> avformat_network_init(); return JNI_VERSION_1_8;}void JNI_OnUnload(JavaVM
> *vm, void *reserved) { (*jniEnv)->DeleteLocalRef(jniEnv, clazzLogger);}*
>
> Le jeu. 24 mars 2022 à 15:55, Dan Egnor <egnor at ofb.net> a écrit :
>
>> On Thu, Mar 24, 2022, 3:59 AM Algarve Branqueira <branqueira at gmail.com>
>> wrote:
>>
>>> I tried this method but it doesn't work with ffmpeg on windows with
>>> mingw.
>>> I must have forgotten a few things.
>>>
>>>  what disturbs me the most is that at the end of the video conversion,
>>> ffmpeg kills its threads for decoding and encoding but we don't have a
>>> simple solution to execute an end method.
>>>
>>> I attached the jvm so I basically need to destroy the thread called a
>>> simple "DetachCurrentThread" method.
>>>
>>> Any idea :)
>>>
>>
>> As you know, my best idea is to rethink your life choices and not try to
>> get log messages attributed to specific instances, instead treating them as
>> a single global stream used for developer diagnostics. I think you're
>> swimming against the flow trying to do anything else.
>>
>> But I don't think you'll find this helpful?
>>
>> -- egnor
>>
>>> _______________________________________________
>> Libav-user mailing list
>> Libav-user at ffmpeg.org
>> https://ffmpeg.org/mailman/listinfo/libav-user
>>
>> To unsubscribe, visit link above, or email
>> libav-user-request at ffmpeg.org with subject "unsubscribe".
>>
>
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