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• Why Do Some of the Codecs in FFMPEG's Supported Codec List Show "encoders :" or "decoders :" in Parenthesis ?

  4 mai 2020, par spaceman

  If you open the Command Prompt, and run ffmpeg -codecs,
  
you will get a long list of Codecs that FFMPEG supports.

  



  Here's a small sample of the list :

  



   DEV.L. h261                 H.261
 DEV.L. h263                 H.263 / H.263-1996, H.263+ / H.263-1998 / H.263 version 2
 D.V.L. h263i                Intel H.263
 DEV.L. h263p                H.263+ / H.263-1998 / H.263 version 2
 DEV.LS h264                 H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10 (encoders: libx264 libx264rgb)
 D.V.LS hevc                 H.265 / HEVC


  



  Now If you briefly go over the whole list,
  
you see that most Codecs in this list appear with their Name and Description,
  
but some of the Codecs also include parenthesis in the Description, and in the parenthesis,
  
they specify "encoders :" or "decoders :".

  



  For example :

  



  1)

  



   DEV.LS h264                 H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10 (encoders: libx264 libx264rgb)


  



  2)

  



   DEVILS jpeg2000             JPEG 2000 (decoders: jpeg2000 libopenjpeg) (encoders: jpeg2000 libopenjpeg)


  



  3)

  



   DEV.L. msmpeg4v3            MPEG-4 part 2 Microsoft variant version 3 (decoders: msmpeg4) (encoders: msmpeg4)


  



  4)

  



   DEA.L. aac                  AAC (Advanced Audio Coding) (encoders: aac libvo_aacenc)


  



  5)

  



   DEA.L. amr_nb               AMR-NB (Adaptive Multi-Rate NarrowBand) (decoders: amrnb libopencore_amrnb) (encoders: libopencore_amrnb)
 DEA.L. amr_wb               AMR-WB (Adaptive Multi-Rate WideBand) (decoders: amrwb libopencore_amrwb) (encoders: libvo_amrwbenc)


  



  My question :

  



  Why do some Codecs have those parenthesis, specifying Encoders/Decoders,
  
while other (in fact : most) codecs don't have these parenthesis ?

  


• avformat/matroskadec : Improve forward compability

  25 mars 2020, par Andreas Rheinhardt

  avformat/matroskadec : Improve forward compability
  Matroska is built around the principle that a reader does not need to
  
  understand everything in a file in order to be able to make use of it ;
  
  it just needs to ignore the data it doesn't know about.
  Our demuxer typically follows this principle, but there is one important
  
  instance where it does not : A Block belonging to a TrackEntry with no
  
  associated stream is treated as invalid data (i.e. the demuxer will try
  
  to resync to the next level 1 element because it takes this as a sign
  
  that it has lost sync). Given that we do not create streams if we don't
  
  know or don't support the type of the TrackEntry, this impairs this
  
  demuxer's forward compability.
  Furthermore, ignoring Blocks belonging to a TrackEntry without
  
  corresponding stream can (in future commits) also be used to ignore
  
  TrackEntries with obviously bogus entries without affecting the other
  
  TrackEntries (by not creating a stream for said TrackEntry).
  Finally, given that matroska_find_track_by_num() already emits its own
  
  error message in case there is no TrackEntry with a given TrackNumber,
  
  the error message (with level AV_LOG_INFO) for this can be removed.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavformat/matroskadec.c

• clang++ : error : linker command failed with exit code 1 (use -v to see invocation) in cpp with ffmpeg

  6 avril 2020, par Pradeep Simba

  clang++: error: linker command failed with exit code 1 (use -v to see invocation)


  



  I saw this link and link2. But, it not done.

  



  My jni folder :

  



  

  



  Android.mk file

  



  LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_C_INCLUDES += ./include
LOCAL_MODULE     := native-lib
LOCAL_CFLAGS := -DSTDC_HEADERS -std=c99
LOCAL_CFLAGS := -Wno-pointer-sign
LOCAL_ARM_MODE := arm
APP_OPTIM := release
LOCAL_SRC_FILES  := \
./native-lib.cpp
LOCAL_LDLIBS := -llog
include $(BUILD_SHARED_LIBRARY)


  



  native-lib.cpp file

  



  #include &#xA;#include <string>&#xA;&#xA;extern "C"&#xA;{&#xA;#include "libavcodec/avcodec.h"&#xA;#include "libavformat/avformat.h"&#xA;#include "libavutil/opt.h"&#xA;}&#xA;&#xA;extern "C" JNIEXPORT jstring JNICALL&#xA;Java_com_example_m_MainActivity_stringFromJNI(&#xA;JNIEnv* env,&#xA;jobject /* this */) {&#xA;std::string hello = "Hello from C&#x2B;&#x2B;";&#xA;av_register_all();&#xA;return env->NewStringUTF(hello.c_str());&#xA;}&#xA;</string>

  



  When I build ndk this error occurs.

  



  D:\Github\n>ndk-build
Android NDK: APP_PLATFORM not set. Defaulting to minimum supported version android-16.
[arm64-v8a] Compile++      : native-lib <= native-lib.cpp
[arm64-v8a] SharedLibrary  : libnative-lib.so
./obj/local/arm64-v8a/objs/native-lib/./libmp3lame/native-lib.o: In function `Java_com_example_m_MainActivity_stringFromJNI':
D:\Github\n/jni/./libmp3lame/native-lib.cpp:16: undefined reference to `av_register_all'
clang++: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [D:/install/sdk/ndk/21.0.6113669/build//../build/core/build-binary.mk:725: obj/local/arm64-v8a/libnative-lib.so] Error 1

D:\Github\n>ndk-build -v
GNU Make 4.2.1
Built for x86_64-w64-mingw32
Copyright (C) 1988-2016 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later /gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

D:\Github\n>


  



  why it comes like this native-lib.cpp:16: undefined reference av_register_all ?

  



  I added all the required libs in my jni folder but, why this error and this native-lib.cpp:16: undefined reference av_register_all comes ?
How can I solve this ?