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Posted: **15 Mar 2017 16:09**

Hello

I was searching around the internet but there are not good examples about using libvlc_media_new_callbacks from stream from an array of data

I am developing a software to play packets form an USB Device on Linux. I actually get to play the data but saving in a file that constantly grows up, that's the problem the file could consume the hard drive if you are reproducing it for a long time, for 48 min of Video i got a file of 10GB, the packets are TS (transport stream packets) so in a single frequency i have 6 programs ID, I just saying in that file of 10GB i have 6 different channels.

Lets see the callback function of the code USB receiving, in that callback function i get the buffer with the data. (I am using Libusb, this function is doing by a thread just receive data, the play is doing in the main thread application)

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//Global variables
std::ofstream variable_archivo_TS ("data.ts");                                          //File to write the BTS frame
const int tamanio_buffer=1024;                                                              //Size of the buffer 240Kb 245760
unsigned char MPEG2_TS[tamanio_buffer];                                            //Buffer to receive
int contador_evitar_basura=0;   


static void funcion_de_llamda_leer_transferencia_usb(struct libusb_transfer *transferencia_usb_2)
{
    int res;
    if(transferencia_usb_2->status ==LIBUSB_TRANSFER_COMPLETED)
    {
        std::cout<<"Transferencia completa"<<std::endl; //Mostar la siguiente advertencia
    }
    else
    {
        std::cout<<"Error: "<<transferencia_usb_2->status<<std::endl;   //Mostar la siguiente advertencia
    }

    contador_evitar_basura++;  //Incrementar contador_evitar_basura

    //If glbal_counter > 2 write to a file, this to avoid the trash in the first transmissions
    if (contador_evitar_basura>2)  variable_archivo_TS.write( (char *)transferencia_usb_2->buffer, tamanio_buffer);

    res = libusb_submit_transfer(transferencia_usb_2); //Realizar unanueva transferencia

    if(res !=0)
    {
        std::cout<<"submitting. error code: "<<res<<std::endl;  //Mostar la siguiente advertencia
    }
}

//This line of the code is where a write to the file.

Code: Select all

if (contador_evitar_basura>2) variable_archivo_TS.write( (char *)transferencia_usb_2->buffer, tamanio_buffer);

In the frontend to play it i wait 1.5 seconds to fill the file, serach the directory and path to the file, add the media and play the file

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SemcoSleep(1500);                                                               //Esperar 1,5 segundo para llenar un poco el archivo .TS

    //Obteniendo el directorio donde se encuentra el archivo a reproducir Comienzo
    char directorio_actual_de_trabajo[200000];                                      //Tamaño del buffer donde guardar el directorio
    getcwd(directorio_actual_de_trabajo, sizeof(directorio_actual_de_trabajo));     //Rellena el buffer con el directorio actual de trabajo
    std::string direccion_archivo_vlc=directorio_actual_de_trabajo;                 //Se guarda en un string
    direccion_archivo_vlc="file://"+direccion_archivo_vlc+"/data.ts";               //Se modifica el string para hacerlo compatible con la direccion tomada por libvlc
    //Obteniendo el directorio donde se encuentra el archivo a reproducir Fin

    libvlc_media_t *media;                                                          //Se crea la variable media
    media = libvlc_media_new_location(instancia_vlc, &direccion_archivo_vlc[0u]);   //fill 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
    libvlc_media_player_play(reproductor);                                          //Reproducir

The question is i could use this function

LIBVLC_API libvlc_media_t* libvlc_media_new_callbacks ( libvlc_instance_t * instance,
libvlc_media_open_cb open_cb,
libvlc_media_read_cb read_cb,
libvlc_media_seek_cb seek_cb,
libvlc_media_close_cb close_cb,
void * opaque
)

In the callback read pass the buffer of 1024bytes incoming through the usb transfer rather than write it to a file

But i can find any code how to implement it. I just find this https://forum.videolan.org/viewtopic.php?t=127796

The source code of my project is here https://github.com/aurquiel/TDA_Linux

Posted: **15 Mar 2017 21:44**

libvlc_media_new_callbacks is meant to stream a media from memory, not from a file. You'd need to remove the intermediate temporary file for this to work I think.

That being said, couldn't you simply open your media using the v4l2 module? You're reading from a device, not memory per-se, and I don't see the need for libvlc_media_new_callbacks here.

Posted: **18 Apr 2017 15:03**

libvlc_media_new_callbacks is meant to stream a media from memory, not from a file. You'd need to remove the intermediate temporary file for this to work I think.

That being said, couldn't you simply open your media using the v4l2 module? You're reading from a device, not memory per-se, and I don't see the need for libvlc_media_new_callbacks here.

I can't use v4I2 because i am developing the software at linux using libusb, i am controlling the device from the user space, that's why i want to use the media_new_callbacks function, for v4I2 i must write a driver for the device, the project works well far now so i don't see the necessity to trow all the development around libusb to write a driver .

I have a question, should i use media_new_callbacks in a new thread with a while loop after call it, or just run it at the main thread of my program and then pass the media to the player to play it?

Posted: **25 Apr 2017 18:48**

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

Code: Select all

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
}

I don't put it in another thread

procedimiento_retardo_milisegundos(60); this is a delay of 60 ms

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