add a way for the user to find gpu driver / device

ecosystem/ffmpeg_plugin/README.md

@@ -196,7 +196,21 @@ enabled gpu_direct:
 ```
 
 #### Additional Notes
-GPU Direct Flag: When compiling FFmpeg with the MTL_GPU_DIRECT feature enabled, ensure that your system's GPU drivers and hardware support direct GPU memory access.
+**GPU Direct Flag:** When compiling FFmpeg with the MTL_GPU_DIRECT feature enabled, ensure that your system's GPU drivers and hardware support direct GPU memory access.  
+GPU device IDs and GPU driver IDs are printed during initialization.
+
+**Options:**
+1. `-gpu_device`
+1. `-gpu_driver`
+
+Both default to 0, but if your device doesn't initialize, adjust it using the information printed during initialization.
+
+**Example:**
+```
+Drivers count: 1
+Driver: 0: Device: 0: Name: Intel(R) Data Center GPU Flex 170, Type: 1, VendorID: 8086, DeviceID: 22208
+```
+
 
 [GPU Documentation](../../doc/gpu.md)
 

ecosystem/ffmpeg_plugin/mtl_st20p_rx.c

@@ -169,9 +169,12 @@ static int mtl_st20p_read_header(AVFormatContext* ctx) {
     /* create context for one gpu device */
     GpuContext gpu_ctx = {0};
 
-    int res = init_gpu_device(&gpu_ctx, s->gpu_driver_index, s->gpu_device_index);
-    if (res < 0) {
-      err(ctx, "%s, app gpu initialization failed %d\n", __func__, res);
+    /* print GPU device and driver IDs */
+    print_gpu_drivers_and_devices();
+
+    ret = init_gpu_device(&gpu_ctx, s->gpu_driver_index, s->gpu_device_index);
+    if (ret < 0) {
+      err(ctx, "%s, app gpu initialization failed %d\n", __func__, ret);
       return -ENXIO;
     }
     ops_rx.gpu_context = (void*)(&gpu_ctx);