Libvlc function libvlc_new_callbacks

aurquiel

Hello i am trying to implement this function of libvlc version 3.0, libvlc_new_callbacks to read from a buffer array. Documentation

I got a function that use libusb to receive usb transfers from a device

static void procedimiento_de_llamada_leer_transferencia_usb(struct libusb_transfer *transferencia_usb_2)
{
    if(transferencia_usb_2->status == LIBUSB_TRANSFER_COMPLETED)             
    {
        std::cout<<"Transferencia completa"<<std::endl;                    
    }
    else std::cout<<"Error: "<<transferencia_usb_2->status<<std::endl;      

    contador_evitar_basura++;                                                 
    if (contador_evitar_basura > 4)                 
    {
        apuntador_al_buffer_recepcion_BTS=transferencia_usb_2->buffer;
        variable_archivo_TS.write( (char *)transferencia_usb_2->buffer, tamanio_buffer); 
    }

    int respuesta_transferencia_llamada = libusb_submit_transfer(transferencia_usb_2);  

    if(respuesta_transferencia_llamada != 0) std::cout<<"Error transferencia: "<<respuesta_transferencia_llamada<<std::endl; 
}

Actually the transfered bytes goes to a file and then open that file with libvlc as a media file to reproduce it, with this line instruction i write the bytes received to a file

variable_archivo_TS.write( (char *)transferencia_usb_2->buffer, tamanio_buffer);

I can see the video in my program but the file is constantly growing, if a keep watching the video for a long time the file could get sizes of 10 Gb. I am trying to send the buffer that libusb received to the player without saving it in a file, i create a global variable that points to the buffer

unsigned char *apuntador_al_buffer_recepcion_BTS;

apuntador_al_buffer_recepcion_BTS=transferencia_usb_2->buffer;

Then i am trying to implement the function of libvlc_new_call_backs:

I pass the pointer apuntador_al_buffer_recepcion_BTS to the function, and set the callbacks open and read, declare seek and close as a NULL, maybe is a wrong approach but i am thinking to read all the buffer at once so i don't need a seek function

void procedimiento_media_callbacks()
{
    static libvlc_media_t *media = libvlc_media_new_callbacks(
                         instancia_vlc,     // vlc
                         open_callback,     //open media
                         read_callback,     //read media
                                  NULL,     //NULL seak
                                  NULL,     //NULL close
     apuntador_al_buffer_recepcion_BTS);    //NULL

    libvlc_media_player_set_media(reproductor, media);
    libvlc_media_add_option(media, funcion_leer_id());    
    libvlc_media_player_set_media(reproductor, media);          

}

I am thinking in just using the open_callback function to points data to opaque(buffer) and set sizep to the size of the buffer,

int open_callback(void *opaque, void **datap, long unsigned int *sizep)
{
    *sizep = 245760;
    *datap = opaque;
    return 0;
}

In the read function i am not sure about this just return the size of data read it

long int read_callback(void *opaque, unsigned char *buf,long unsigned int len)
{
    return 245760;
}

But i can't get it work, i couldn't find a code that use this function.

Maybe if you know another way to read directly from the buffer, without creating a file, tell me please.

jsulm

@aurquiel This is a Qt forum.
How is your question related to Qt?

VRonin

Pure speculation:

variable_archivo_TS.write( (char *)transferencia_usb_2->buffer, tamanio_buffer); looks like you are not cleaning the buffer after any call

aurquiel

@VRonin said in Libvlc function libvlc_new_callbacks:

Pure speculation:

variable_archivo_TS.write( (char *)transferencia_usb_2->buffer, tamanio_buffer); looks like you are not cleaning the buffer after any call

Thank you

By the way i share the solution for other users, they could improve it

At this way you will read from a buffer that comes from libusb with transport stream video

int open_callback(void *opaque, void **datap, long unsigned int *sizep)
{
    *sizep = 245760;
    *datap = opaque;
    return 0;
}

long int read_callback(void *opaque, unsigned char *buf,long unsigned int len)
{
    procedimiento_retardo_milisegundos(60);                         //Delay waiting new data
    std::memcpy(buf,apuntador_al_buffer_recepcion_BTS, 245760);     //Copy from archive
    return 245760;
}

void procedimiento_media_callbacks()
{
    static libvlc_media_t *media = libvlc_media_new_callbacks(
                         instancia_vlc,     //Instancia vlc
                         open_callback,     //open media
                         read_callback,     //read media
                                  NULL,     //NULL seak
                                  NULL,     //NULL close
     apuntador_al_buffer_recepcion_BTS);    //NULL

    libvlc_media_player_set_media(reproductor, media);
    libvlc_media_add_option(media, funcion_leer_id());                                      //Se coloca el Id del canal deseado a reproducir
    libvlc_media_player_set_media(reproductor, media);                                      //Se coloca el medio media en el reporductor
}

_PIB

@jsulm if one cannot posts something about C++ and not directly related to Qt what is "General and Desktop" category of "Qt Development" for?

jsulm

@_PIB You can ask but you should be aware that this is Qt forum.
"General and Desktop" - Qt in general and desktop related questions.

_PIB

@jsulm I mean, there is a development category which has "Qt" in it's name and a development category which does not have "Qt" in it's name. It would be natural to suggest that If it's the only difference then one can post things about C+++ and not necessarily about Qt here.

jsulm

@_PIB You should ask C++ questions here: https://forum.qt.io/category/34/c-gurus
It would be more natural to ask VLC related questions in a VLC forum/mailing list.