![]() ![]() Moreover, if we want to show 24 frames per second(FPS): 5.9 MB * 24 = ~141.6 MB per one second. The size of each pixel is 3 bytes because RGB has 3 color channels by 1 byte. One frame is a matrix that contains info about each pixel. It is the most popular codec for a video that is used in Android. So, if you want to do remuxing you have to use libavformat, which depends on other libraries: ![]() The libswscale is a library containing video image scaling routines and provides a fast and modular scaling interface.The libswresample library is capable of handling different sample formats, sample rates and a different number of channels and different channel layout.The libpostproc is a library containing video postprocessing routines.The libavutil is a helper library containing routines for different parts of FFmpeg.The libavdevice is a special devices muxing/demuxing library and is a complement to libavformat library.The libavfilter is a library of filters that provides the media filtering layer.The libavformat is a library containing demuxers and muxers for audio/video container formats.The libavcodec is a library of codecs for decoding and encoding multimedia.And if you want to change video resolution, you have to edit video frames which you retrieve after decoding. For instance, if all you need is just trim video you have to do only remuxing and edit FFmpeg’s AVPackets after demuxing. You can choose first or second variant depends on your task. The video processing is process of manipulation of encoded packets or decoded frames/samples. The transcoding is the process that includes 4 steps: demuxing, decoding, encoding and muxing. It is called “raw” because they contain unprocessed (or minimally processed) raw data from an image sensor. The raw video data is a sequence of pictures. The result of this process is a pulse code modulation format, abbreviated PCM. This process is known as analog-to-digital conversion. So, we have to convert the analog signal into a series of numbers representing its amplitude. It is valued vary continuously, and the signal exists at every point in time. What is the raw audio data?Īfter audio recording, we have an analog signal. I clarify the reason why we should encode data below. So, files with *.mp3 extensions which we use every day are audio data that was encoded using the mp3 codec. The most popular codec for video is H.264. The extension of the file is a name of the container.Ĭontainers contain encoded data. In simple words, *.mp4, *.avi or *.flv files are containers, because they hold different types of data. The container is specification describes how different elements of data and metadata coexist in a file. Demultiplexing means splitting from the container the video and audio out into separate streams. Multiplexing means combining different types, for instance, audio and video, of data in a container. They are shorts for multiplexing and demultiplexing. Let me know if you have any doubts on this in comments.Remuxing is a process that includes two other ones: demuxing and muxing. We can use android C/C++ libraries like liblog to print output in logcat from C. We don’t have to compile binaries static, so size of binary will be reduced.Ģ. $ export PATH=$PATH:/ $ ndk-buildīy executing “ndk-build”, ndk will compile our test.c (not static) and puts the binary in hello_world/libs/armeabi/ġ. ![]() $ gedit Android.mk # write Android.mk contents, save and exit. $ mkdir ~/hello_world/ $ mkdir ~/hello_world/jni $ mkdir ~/hello_world/libs $ cd ~/hello_world/jni/ $ gedit test.c # create your C code in file, save and exit. Now, place test.c and Android.mk file in jni directory. So, we need to create a directory structure like this The NDK system is only able to compile in android project hierarchy. LOCAL_PATH := $(call my-dir) include $(CLEAR_VARS) # give module name LOCAL_MODULE := hello_world # list your C files to compile LOCAL_SRC_FILES := test.c # this option will build executables instead of building library for android application. Now, to compile it with NDK, we need a Android.mk. So, above program will just print “Hello World” on standard output. Let’s create a simple hello world C program in file test.c ![]() Let’s take an example to see how it works. So, I found an alternative (and proper) way to build C/C++ executable using Android NDK. that is not the most convenient way to compile means I don’t want to compile my binary every time static. Yes, with this method we can only compile static binaries. Using above command, we can compile a C file named test.c as a static binary. I was wandering if I can compile C binary that runs on android platform, So a long time ago I found a method (without using ndk), withĪrm-none-linux-gnueabi-gcc -static test.c -o test ![]()
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