Posts From Category: general

On windows when you will try to display \033[0m or \x1B[31m and so one, instead of getting color in terminal you will get ]31m. On windows 10 and letter it’s pretty easy to fix. You just need to include next code:

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#include <windows.h>

HANDLE hConsole = GetStdHandle(STD_OUTPUT_HANDLE);
if (hConsole)
{
    DWORD consoleMode;
    GetConsoleMode(hConsole, &consoleMode);
    SetConsoleMode(hConsole, consoleMode | ENABLE_VIRTUAL_TERMINAL_PROCESSING);
}

// now you can use color printf()

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One of the previous projects was related to bringing up our newly developed board with the AmLogic s805x SoC CPU board. I will describe how the proccess of bringing up looks like, what was tested and also we will take a look how the AmLogic board flashing proccess is carried out for GXL platform (G12B and more recent are very similar). This is our board:

The first stage of bringup is to build image for reference board. Our case is p241. We took a113 sources for this. Build p241 reference sources:

Build image

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# You need arm-linux-gnueabihf-gcc and aarch64-linux-gnu-gcc to be installed in system toolchains
$ sudo apt-get install zlib1g zlib1g-dev
$ source buildroot/build/setenv.sh
# Choose “mesongxl_p241_32_kernel49” // 37
$ ln -s aml-4.9 kernel/aml-3.14
$ ln -s aml-4.9 hardware/aml-3.14
$ make

After the proccess in complete everything will be at output/mesongxl_p241_32_kernel49/images with folowing parts:

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“C_INCLUDES must be under the source or output directories” error can indicate the the sources not included under LOCAL_C_INCLUDES

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LOCAL_C_INCLUDES += \
    $(LOCAL_PATH) \
    $(LOCAL_PATH)/src

But at the same time be aware of symlinks! The problem can be if the folder created with symlinks! So aware of them.

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How to avoid usage of libgcc_s_seh-1.dll or libgcc_s_dw2-1.dll ? You need to include following link flags:

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-static-libgcc -static-libstdc++ -static

In case of CMake:

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if(MINGW)
    SET(CMAKE_EXE_LINKER_FLAGS  "${CMAKE_EXE_LINKER_FLAGS} -static-libgcc -static-libstdc++ -static")
endif()

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You can simply get current arch usign following code, where on windows can be used GetNativeSystemInfo() and on macos and linux uname() function:

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std::string GetOSArch()
{
#ifdef CPK_OS_WIN
    SYSTEM_INFO info;
    GetNativeSystemInfo(&info);
    switch (info.wProcessorArchitecture) {
        case PROCESSOR_ARCHITECTURE_AMD64:
            return "x86_64";
        case PROCESSOR_ARCHITECTURE_INTEL:
            return "x86";
        case PROCESSOR_ARCHITECTURE_IA64:
            return "ia64";
    };
#endif
#if defined(CPK_OS_LINUX) || defined(CPK_OS_MACOS)
    long ret = -1;
    struct utsname u;

    if (ret == -1)
        ret = uname(&u);
    if (ret != -1) {
        if (strlen(u.machine) == 4 && u.machine[0] == 'i'
                && u.machine[2] == '8' && u.machine[3] == '6')
            return std::string("x86");
        if (strcmp(u.machine, "amd64") == 0) // Solaris
            return std::string("x86_64");

        return std::string(u.machine);
    }
#endif
    return "";
}

OS detection can be done for example on cmake side or with other definition like __WIN32:

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if(WIN32)
    add_definitions(-DCPK_OS_WIN)
else()
    if (${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
        add_definitions(-DCPK_OS_MACOS)
    else()
        add_definitions(-DCPK_OS_LINUX)
    endif()
endif()

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For example you install new compiler or MinGW C++ and you met error of _zst28__throw_bad_array_new_lengthv after compile time. You can verify you compiler with simple example:

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#include <iostream>
#include <vector>

using namespace std;
int main(void)
{
    vector <int> a = {2, 0, 1}; // problem line
    cout << "hellow world";
    return 0;
}

If you still get error on such simple example you have system libstd++ missmatch. Your system is taking this library from some other part of the system (NOT from compiler directory) of the %PATH% location. Edit you PATH variable and make compiler directory (for example: c:\mingw64\bin) to be ABOVE the problematic one. Or with other words: compiler directory must have more priority. Very popular problematic place is git - C:\Git\mingw64\bin, move it to the end of %PATH%.

The error must go away.

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Exploring GStreamer and pipelines

Before proceeding to code review, let’s look at what we can do without it. GStreamer includes useful utilities to work with, in particular:

• gst-inspect-1.0 will allow you to see a list of available codecs and modules, so you can immediately see what will do with it and select a set of filters and codecs.
• gst-launch-1.0 allows you to start any pipeline. GStreamer uses a decoding scheme where a stream passes through different components in series, from source to sink output. You can choose anything as a source: a file, a device, the output (sink) also may be a file, a screen, network outputs, and protocols (like RTP).

Simple example of using gst-launch-1.0 to connect elements and play audio:

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gst-launch-1.0 filesrc location=/path/to/file.ogg ! decodebin ! alsasink

Filesrc will open file, decodebin - decode it, and alsasink will output audio.

Another more complex example of playing an mp4 file:

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gst-launch-1.0 filesrc location=file.mp4 ! qtdemux ! h264parse ! avdec_h264 ! videoconvert ! autovideosink

The input accepts the mp4 file, which goes through the mp4 demuxer — qtdemux, then through the h264 parser, then through the decoder, the converter, and finally, the output.

You can replace autovideosink with filesink with a file parameter and output the decoded stream directly to the file.

Programming an application with GStreamer C/C++ API. Let’s try to decode

Now when we know how to use gst-launch-1.0, we are doing the same thing within our application. The principle remains the same: we are building in a decoding pipeline, but now we are using the GStreamer library and glib-events.

We will consider a live example of H264 decoding.

Initialization of the GStreamer application takes place once with the help of

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gst_init (NULL, NULL);

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After a long thought, I finally decided to switch my blog articles to english, and continue to give some rare and mostly unintresting info in free form. And today we will talk more about Android, NDK and some undocumentated video/audio functionality, maybe will discover some new knowlage about AAC and maybe it will help your own problem, like it was for me. In a focus of this acrticle is Android AAC decoder, and a little detail how the decoding in android working behind NDK documentation.

AMediaCodec using steps

First let take a very very surface look how to start decoding using NDK:

1. Create AMediaCodec using codec name.
2. Configure AMediaCodec via AMediaCodec_configure.
3. Ctart decoding AMediaCodec_start.
4. Give a buffer using AMediaCodec_getInputBuffer.
5. Back buffer with AMediaCodec_queueInputBuffer.
6. Repeat while you have an buffer ;).

Looks very simple, and work good as well. I can end this article in this place, but I don’t tell you nothing about buffer requirenments and other stuffs, and in NDK/SDK also all simple like that. So what going on behind this android decoding? What if you getting some error with your buffer, or you don’t have sound in some rare cases? How the Android decoder works like, let take a look at AAC audio decoder as example. Let’s begin from simple.

As you see on this bad jpeg picture :) Android have different implementation of AAC decoders as OMX components. But that’s not all, beside some software implemetation on some platforms existed hardware implementation, like on Broadcom chips. Keep at mind, and will transport to SoftAAC2 decoder. Let take a look deeper.

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In some cases you want close the window on windows with ctrl+c combination, or invoke event for different reasons. On windows you can make such small program:

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#include <windows.h>
#include <stdio.h>

int main(int argc, char* argv[])
{
 int pid = atoi( argv[1] );
 printf("kill in console %d", pid);

 FreeConsole();
 if (AttachConsole(pid))
 {
     SetConsoleCtrlHandler(NULL, true);
     GenerateConsoleCtrlEvent(CTRL_C_EVENT, 0);
     FreeConsole();
     SetConsoleCtrlHandler(NULL, false);
 }


 return 0;
}

As argument you can pass a pid or the window proccess. (You can get it via system monitor).

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What I often dislike about the standard documentation for many things is that seemingly identical items are separated by a huge layer of unnecessary information, or are generally so poorly documented that it’s faster to find the answer on Stack Overflow. So, if we know what Electron is, and roughly imagine that it consists of a main process controlled by node-js and a browser process (the so-called render process), how do we organize communication between 2 processes?

Main process communication -> Render process (from main to render)

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// main.process.js - send
// mainWindow - this is BrowserWindow
mainWindow.webContents.send('message', data); // отправка

// render.process.js - recive
import { ipcRenderer } from 'electron';
ipcRenderer.on('message', (event, data) => {
// handle
});

Communication between Render process -> Main process (from render to main)

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// main.process.js - recive
import { ipcMain } from "electron";
ipcMain.on('message', (event, data) => {
// handle
})

// render.process.js - send
import { ipcRenderer } from 'electron';
ipcRenderer.send('message', data);

global object

Why it was so difficult to collect this information in one place I don’t understand at all. There is also a useful shared global object that is available inside the renderer and is declared in the main process.

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// main.process.js
global.a = 1

// render.process.js
import { remote } from 'electron';
remote.getGlobal('a') // 1

Maybe someone will find this information useful

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Hello everyone this is my updated blog page. Here I will post my post about programming (C/C++/Java/Python), music engineering and other life stuffs. So everyone are welcome.

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