OpenVisualCloud · dmkarthi · Jul 23, 2026 · Jul 21, 2026 · Jul 21, 2026 · Jul 23, 2026
diff --git a/README.md b/README.md
@@ -109,6 +109,7 @@ FFmpeg is an open source project licensed under LGPL and GPL. See https://www.ff
     ```bash
     sudo apt-get install -y xserver-xorg-video-dummy ubuntu-desktop
     ```
+  - The stock `mtl_st20p` muxer only exposes `p_port`/`r_port` (2 physical NIC ports). To use more than 2 NICs with the default (non-`ENABLE_MTL_TX`) build, the plugin's `libavdevice/mtl_common.h` must be patched to add `p2_port`..`p7_port` (and matching `p2_sip`..`p7_sip`) AVOptions mapped to `devArgs.port[MTL_PORT_2..MTL_PORT_7]` / `devArgs.sip[...]`, then FFmpeg rebuilt and reinstalled. Without this patch, `nic_count` is effectively capped at 2 for the FFmpeg TX path (the `ENABLE_MTL_TX` direct-pipeline build already supports up to 8 NICs without any patch).
 
 ### Build Steps
 
@@ -143,7 +144,8 @@ dvledtx uses a JSON config file with three sections:
 | Section | Field | Description |
 |---------|-------|-------------|
 | **log_file** | `log_file` | (Optional) Path/name of the log output file (e.g. `dvledtx.log`). If omitted, logging goes to console only. |
-| **interfaces[]** | `name` | PCI BDF address of the NIC (e.g. `0000:06:00.0`) |
+| **interfaces[]** | `nic_index` | (Optional) Must equal this entry's position in the `interfaces[]` array (0, 1, 2, ...); parsing fails if it doesn't match. Informational/self-documenting only — interfaces are always resolved by array position. |
+| | `name` | PCI BDF address of the NIC (e.g. `0000:06:00.0`) |
 | | `sip` | Source IP address |
 | | `dip` | Destination multicast IP address |
 | **video** | `width` | Source frame width in pixels |
@@ -165,8 +167,8 @@ dvledtx uses a JSON config file with three sections:
 {
   "log_file": "dvledtx.log",
   "interfaces": [
-    { "name": "0000:03:10.0", "sip": "192.168.50.30", "dip": "239.168.85.20" },
-    { "name": "0000:03:10.2", "sip": "192.168.50.29", "dip": "239.168.85.21" }
+    { "nic_index": 0, "name": "0000:03:10.0", "sip": "192.168.50.30", "dip": "239.168.85.20" },
+    { "nic_index": 1, "name": "0000:03:10.2", "sip": "192.168.50.29", "dip": "239.168.85.21" }
   ],
   "video": {
     "width": 1920, "height": 1080,
@@ -348,6 +350,8 @@ pkill -f "gnome-session --session=ubuntu"
 sudo pkill -f "Xorg :99"
 ```
 
+`interfaces[]` supports up to 8 NICs (MTL's port limit); each `tx_sessions[]` entry picks its NIC via `nic_index` (see `config/tx_fullhd_multi_nic.json` for an 8-NIC/8-session example). Using more than 2 NICs with the default FFmpeg TX path requires the patched `mtl_st20p` muxer described above.
+
 ## Logging
 
 dvledtx includes a built-in logger with configurable output targets and log levels.

diff --git a/config/tx_1session_12bit.json b/config/tx_1session_12bit.json
@@ -1,6 +1,7 @@
 {
   "interfaces": [
     {
+      "nic_index": 0,
       "name": "0000:06:00.0",
       "sip":  "192.168.50.29",
       "dip":  "239.168.85.20"
@@ -17,6 +18,7 @@
   },
   "tx_sessions": [
     {
+      "nic_index":    0,
       "udp_port":     20000,
       "payload_type": 96,
       "crop": { "x": 0, "y": 0, "w": 1920, "h": 1080 }

diff --git a/config/tx_2k_multi_session.json b/config/tx_2k_multi_session.json
@@ -2,6 +2,7 @@
   "log_file": "dvledtx.log",
   "interfaces": [
     {
+      "nic_index": 0,
       "name": "0000:03:00.1",
       "sip":  "192.168.50.29",
       "dip":  "239.168.85.20"
@@ -20,16 +21,19 @@
   },
   "tx_sessions": [
     {
+      "nic_index":    0,
       "udp_port":     20000,
       "payload_type": 96,
       "crop": { "x": 0,    "y": 0, "w": 854, "h": 1440 }
     },
     {
+      "nic_index":    0,
       "udp_port":     20002,
       "payload_type": 96,
       "crop": { "x": 854,  "y": 0, "w": 854, "h": 1440 }
     },
     {
+      "nic_index":    0,
       "udp_port":     20004,
       "payload_type": 96,
       "crop": { "x": 1708, "y": 0, "w": 852, "h": 1440 }

diff --git a/config/tx_2k_single_session.json b/config/tx_2k_single_session.json
@@ -2,6 +2,7 @@
   "log_file": "dvledtx.log",
   "interfaces": [
     {
+      "nic_index": 0,
       "name": "0000:03:00.1",
       "sip":  "192.168.50.29",
       "dip":  "239.168.85.20"
@@ -20,7 +21,8 @@
   },
   "tx_sessions": [
     {
-      "udp_port":     20000,
+      "nic_index": 0,
+      "udp_port":  20000,
       "crop": { "x": 0, "y": 0, "w": 2560, "h": 1440 }
     }
   ]

diff --git a/config/tx_4k_multi_session.json b/config/tx_4k_multi_session.json
@@ -2,6 +2,7 @@
   "log_file": "dvledtx.log",
   "interfaces": [
     {
+      "nic_index": 0,
       "name": "0000:03:00.1",
       "sip":  "192.168.50.29",
       "dip":  "239.168.85.20"
@@ -20,16 +21,19 @@
   },
   "tx_sessions": [
     {
+      "nic_index":    0,
       "udp_port":     20000,
       "payload_type": 96,
       "crop": { "x": 0,    "y": 0, "w": 640, "h": 1080 }
     },
     {
+      "nic_index":    0,
       "udp_port":     20002,
       "payload_type": 96,
       "crop": { "x": 640, "y": 0, "w": 640, "h": 1080 }
     },
     {
+      "nic_index":    0,
       "udp_port":     20004,
       "payload_type": 96,
       "crop": { "x": 1280, "y": 0, "w": 640, "h": 1080 }

diff --git a/config/tx_4k_single_session.json b/config/tx_4k_single_session.json
@@ -2,6 +2,7 @@
   "log_file": "dvledtx.log",
   "interfaces": [
     {
+      "nic_index": 0,
       "name": "0000:03:00.1",
       "sip":  "192.168.50.29",
       "dip":  "239.168.85.20"
@@ -20,6 +21,7 @@
   },
   "tx_sessions": [
     {
+      "nic_index":    0,
       "udp_port":     20000,
       "payload_type": 96,
       "crop": { "x": 0, "y": 0, "w": 900, "h": 600 }

diff --git a/config/tx_fullhd_multi_nic.json b/config/tx_fullhd_multi_nic.json
@@ -2,40 +2,58 @@
   "log_file": "dvledtx.log",
   "interfaces": [
     {
-      "name": "0000:03:10.0",
-      "sip":  "192.168.50.30",
-      "dip":  "239.168.85.20"
+      "nic_index": 0,
+      "name": "0000:01:10.1",
+      "sip":  "192.168.50.40",
+      "dip":  "239.168.85.30"
+    },
+    {
+      "nic_index": 1,
+      "name": "0000:01:10.3",
+      "sip":  "192.168.50.41",
+      "dip":  "239.168.85.31"
+    },
+    {
+      "nic_index": 2,
+      "name": "0000:01:10.5",
+      "sip":  "192.168.50.42",
+      "dip":  "239.168.85.32"
     },
     {
-      "name": "0000:03:10.2",
-      "sip":  "192.168.50.31",
-      "dip":  "239.168.85.21"
+      "nic_index": 3,
+      "name": "0000:01:10.7",
+      "sip":  "192.168.50.43",
+      "dip":  "239.168.85.33"
     },
     {
-      "name": "0000:03:10.4",
-      "sip":  "192.168.50.32",
-      "dip":  "239.168.85.22"
+      "nic_index": 4,
+      "name": "0000:01:11.1",
+      "sip":  "192.168.50.44",
+      "dip":  "239.168.85.34"
     },
     {
-      "name": "0000:03:10.6",
-      "sip":  "192.168.50.33",
-      "dip":  "239.168.85.23"
+      "nic_index": 5,
+      "name": "0000:01:11.3",
+      "sip":  "192.168.50.45",
+      "dip":  "239.168.85.35"
     },
     {
-      "name": "0000:03:11.0",
-      "sip":  "192.168.50.34",
-      "dip":  "239.168.85.24"
+      "nic_index": 6,
+      "name": "0000:01:11.5",
+      "sip":  "192.168.50.46",
+      "dip":  "239.168.85.36"
     },
     {
-      "name": "0000:03:11.2",
-      "sip":  "192.168.50.35",
-      "dip":  "239.168.85.25"
+      "nic_index": 7,
+      "name": "0000:01:11.7",
+      "sip":  "192.168.50.47",
+      "dip":  "239.168.85.37"
     }
   ],
   "video": {
     "width":  1920,
     "height": 1080,
-    "tx_url": "ball_fullhd_yuv422p10_30fps_5min.mp4"
+    "tx_url": "bbb_sunflower_1080p_30fps_normal.mp4"
   },
   "tx_video": {
     "scale_width":  1920,
@@ -48,20 +66,51 @@
       "nic_index": 0,
       "udp_port":  20000,
       "payload_type": 96,
-      "crop": { "x": 0,    "y": 0, "w": 640, "h": 1080 }
+      "crop": { "x": 0,    "y": 0, "w": 240, "h": 1080 }
     },
     {
       "nic_index": 1,
       "udp_port":  20002,
       "payload_type": 96,
-      "crop": { "x": 640,  "y": 0, "w": 640, "h": 1080 }
+      "crop": { "x": 240,  "y": 0, "w": 240, "h": 1080 }
     },
     {
       "nic_index": 2,
       "udp_port":  20004,
       "payload_type": 96,
-      "crop": { "x": 1280, "y": 0, "w": 640, "h": 1080 }
+      "crop": { "x": 480,  "y": 0, "w": 240, "h": 1080 }
+    },
+    {
+      "nic_index": 3,
+      "udp_port":  20006,
+      "payload_type": 96,
+      "crop": { "x": 720,  "y": 0, "w": 240, "h": 1080 }
+    },
+    {
+      "nic_index": 4,
+      "udp_port":  20008,
+      "payload_type": 96,
+      "crop": { "x": 960,  "y": 0, "w": 240, "h": 1080 }
+    },
+    {
+      "nic_index": 5,
+      "udp_port":  20010,
+      "payload_type": 96,
+      "crop": { "x": 1200, "y": 0, "w": 240, "h": 1080 }
+    },
+    {
+      "nic_index": 6,
+      "udp_port":  20012,
+      "payload_type": 96,
+      "crop": { "x": 1440, "y": 0, "w": 240, "h": 1080 }
+    },
+    {
+      "nic_index": 7,
+      "udp_port":  20014,
+      "payload_type": 96,
+      "crop": { "x": 1680, "y": 0, "w": 240, "h": 1080 }
     }
   ]
 }
 
+
diff --git a/config/tx_fullhd_multi_session.json b/config/tx_fullhd_multi_session.json
@@ -2,6 +2,7 @@
   "log_file": "dvledtx.log",
   "interfaces": [
     {
+      "nic_index": 0,
       "name": "0000:03:10.1",
       "sip":  "192.168.50.29",
       "dip":  "239.168.85.21"
@@ -20,16 +21,19 @@
   },
   "tx_sessions": [
     {
+      "nic_index":    0,
       "udp_port":     20000,
       "payload_type": 96,
       "crop": { "x": 0,    "y": 0, "w": 640, "h": 1080 }
     },
     {
+      "nic_index":    0,
       "udp_port":     20002,
       "payload_type": 96,
       "crop": { "x": 640,  "y": 0, "w": 640, "h": 1080 }
     },
     {
+      "nic_index":    0,
       "udp_port":     20004,
       "payload_type": 96,
       "crop": { "x": 1280, "y": 0, "w": 640, "h": 1080 }

diff --git a/config/tx_fullhd_screen_capture.json b/config/tx_fullhd_screen_capture.json
@@ -1,6 +1,7 @@
 {
   "interfaces": [
     {
+      "nic_index": 0,
       "name": "0000:06:00.0",
       "sip": "192.168.50.29",
       "dip": "239.168.85.20"
@@ -18,6 +19,7 @@
   },
   "tx_sessions": [
     {
+      "nic_index": 0,
       "udp_port": 20000,
       "payload_type": 96,
       "crop": { "x": 0, "y": 0, "w": 1920, "h": 1080 }

diff --git a/config/tx_fullhd_screen_capture_multi_session.json b/config/tx_fullhd_screen_capture_multi_session.json
@@ -1,6 +1,7 @@
 {
   "interfaces": [
     {
+      "nic_index": 0,
       "name": "0000:06:00.0",
       "sip":  "192.168.50.29",
       "dip":  "239.168.85.20"
@@ -18,16 +19,19 @@
   },
   "tx_sessions": [
     {
+      "nic_index":    0,
       "udp_port":     20000,
       "payload_type": 96,
       "crop": { "x": 0,    "y": 0, "w": 640, "h": 1080 }
     },
     {
+      "nic_index":    0,
       "udp_port":     20002,
       "payload_type": 96,
       "crop": { "x": 640,  "y": 0, "w": 640, "h": 1080 }
     },
     {
+      "nic_index":    0,
       "udp_port":     20004,
       "payload_type": 96,
       "crop": { "x": 1280, "y": 0, "w": 640, "h": 1080 }

diff --git a/config/tx_fullhd_single_session.json b/config/tx_fullhd_single_session.json
@@ -2,24 +2,26 @@
   "log_file": "dvledtx.log",
   "interfaces": [
     {
-      "name": "0000:06:00.0",
+      "nic_index": 0,
+      "name": "0000:01:11.3",
       "sip":  "192.168.50.29",
       "dip":  "239.168.85.20"
     }
   ],
   "video": {
     "width":  3840,
     "height": 2160,
-    "tx_url": "ball_fullhd_yuv422p10_30fps_5min.mp4"
+    "tx_url": "bbb_sunflower_1080p_30fps_normal.mp4"
   },
   "tx_video": {
-    "scale_width":  3840,
-    "scale_height": 2160,
+    "scale_width":  1920,
+    "scale_height": 1080,
     "fps":    30,
     "fmt":    "yuv422p10le"
   },
   "tx_sessions": [
     {
+      "nic_index":    0,
       "udp_port":     20000,
       "payload_type": 96,
       "crop": { "x": 0, "y": 0, "w": 1920, "h": 1080 }

diff --git a/include/ffmpeg/ffmpeg_tx.h b/include/ffmpeg/ffmpeg_tx.h
@@ -38,6 +38,14 @@
  *   Also pre-allocates enc_frame (crop-width scratch) and enc_pkt
  *   (contiguous packed frame buffer) whose size must equal MTL's frame_size.
  *
+ *   Multi-NIC: on the session that opens first (idx 0), also registers
+ *   every other configured NIC (up to DVLEDTX_MAX_NICS = 8, MTL's port
+ *   limit) with the mtl_st20p plugin's singleton MTL device via the
+ *   p_port/r_port/p2_port..p7_port AVOptions, since mtl_init()/DPDK EAL is
+ *   only ever invoked once per process. Requires a patched mtl_st20p muxer
+ *   exposing p2_port..p7_port (see README's FFmpeg prerequisite section);
+ *   without it, only 2 NICs (p_port/r_port) can be registered.
+ *
  * close_ffmpeg_tx():
  *   Writes the AVFormat trailer (mtl_st20p: no-op), frees the AVFormatContext
  *   (this destroys the MTL TX session internally), and releases enc_frame/pkt.