[MLT] Analysis of MLT Multimedia Framework Production and Consumption Architecture (3)

premise

1. By reading [MLT] Analysis of MLT Multimedia Framework Production and Consumption Architecture (1), the following two points are satisfied:
   1. Understand the hierarchical relationship of MLT's core C++ packaging
   2. Master using MLT's Consumer (sdl) to consume Producer (MP4)
2. By reading [MLT] Analysis of MLT Multimedia Framework Production and Consumption Architecture (2), the following two points are satisfied:
   1. Understand Service (service abstract base class) and Filter (filter abstract service class)
   2. Master adding Filter to Producer

What can I get from this article?

This article will transform the width and height attributes of the filter attached to the producer on the basis of [MLT] MLT Multimedia Framework Production and Consumption Architecture Analysis (2) , as shown below:

Core class analysis

Properties

[MLT] Analysis of the production and consumption architecture of the MLT multimedia framework (1) simply demonstrates the simple process of the producer (initialized as a video resource) being consumed by the consumer (initialized as SDL). [MLT] Analysis of MLT Multimedia Framework Production and Consumption Architecture (2) In (1), the video producer is simply processed and a video filter is added. As shown in the figure above, this section introduces a new encapsulation for the filter setting properties: Properties (property class) , which provides a general mechanism for communicating with the Service, and we can manipulate and serialize the Service state . This section only briefly introduces the methods we are going to use, and we will fully analyze the property encapsulation later.

// 属性类

// 此类重载了大量的序列化的方法，供各种各样的场景使用
/**
* @brief set   序列化方法
* @param name  要设置的属性key
* @param value 属性值(char*)
* @return      是否设置成功的错误码
*/
int set( const char *name, const char *value );
/**
* @brief set_string   序列化方法
* @param name         要设置的属性key
* @param value        属性值(char*)
* @return             是否设置成功的错误码
*/
int set_string( const char *name, const char *value );
/**
* @brief set     序列化方法
* @param name    要设置的属性key
* @param value   属性值(int)
* @return        是否设置成功的错误码
*/
int set( const char *name, int value );
/**
* @brief set     序列化方法
* @param name    要设置的属性key
* @param value   属性值(int64_t)
* @return        是否设置成功的错误码
*/
int set( const char *name, int64_t value );
/**
* @brief set     序列化方法
* @param name    要设置的属性key
* @param value   属性值(double)
* @return        是否设置成功的错误码
*/
int set( const char *name, double value );
/**
* @brief set       序列化方法
* @param name      要设置的属性key
* @param value     属性值(double)
* @param size      默认传0
* @param destroy   析构方法
* @param serial    序列化方法
* @return          是否设置成功的错误码
*/
int set( const char *name, void *value, int size, mlt_destructor destroy = NULL, mlt_serialiser serial = NULL );
/**
* @brief set       序列化方法
* @param name      要设置的属性key
* @param value     属性值(mlt_color)
* @return          是否设置成功的错误码
*/
int set( const char *name , mlt_color value );
/**
* @brief set       序列化方法
* @param name      要设置的属性key
* @param value     属性值(mlt_rect)
* @return          是否设置成功的错误码
*/
int set( const char *name, mlt_rect value );
/**
* @brief set       序列化方法
* @param name      要设置的属性key
* @param x         x值
* @param y         y值
* @param w         width值
* @param h         height值
* @param opacity   opacity值
* @return          是否设置成功的错误码
*/
int set( const char *name, double x, double y, double w, double h, double opacity = 1.0 );
/**
* @brief set           序列化方法
* @param name          要设置的属性key
* @param properties    属性值(Properties)
* @return
*/
int set( const char *name, Properties& properties );

Add filters for producers

// 创建马赛克滤镜
Mlt::Filter *filter = new Mlt::Filter(profile, "frei0r.pixeliz0r");
// 使用从属性类继承的序列化能力对马赛克滤镜的宽高属性进行设置
filter->set(qUtf8Printable("0"), 0.000); // width不做变化
filter->set(qUtf8Printable("1"), 0.300); // height做变化
// 使用从父类Service中继承的订阅能力添加滤镜
producer.attach(*filter);

Demon display

Modify the Filter (mosaic) effect

1. The filter is only set to width
   
2. The filter is only set for height
   

code

    Profile profile; // defaults to dv_pal
    Producer producer(profile, filename);
    Consumer consumer(profile); // defaults to sdl
      
    Mlt::Filter *filter = new Mlt::Filter(profile, "frei0r.pixeliz0r");
    filter->set(qUtf8Printable("0"), 0.300); 
    filter->set(qUtf8Printable("1"), 0.300);
    producer.attach(*filter);

    // Prevent scaling to the profile size.
    // Let the sdl consumer do all scaling.
    consumer.set("rescale", "none");

    // Automatically exit at end of file.
    consumer.set("terminate_on_pause", 1);

    consumer.connect(producer);
    consumer.run();
    consumer.stop();

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References

[1] MLT github link