RaspPi 4 (64-bit Docker)-Hardware transcoding detection fails although FFmpeg can successfully use h264_v4l2m2

[lugaidvii 0]

# Raspberry Pi 4 (ARM64 Docker) - Hardware transcoding detection fails although FFmpeg successfully uses h264_v4l2m2m

## Environment

### Emby Version

4.9.3.0

### Container

Official Emby ARM64 Docker container

### Host OS

Ubuntu 24.04.4 LTS

Kernel:

```text
Linux 6.12.87+rpt-rpi-v8
```

### Hardware

```text
Raspberry Pi 4
ARM64
4-core Cortex-A72
```

---

## Problem

Emby does not detect any hardware video encoders or decoders.

The Hardware Detection log only reports software codecs:

```json
"VideoDecoders": {},

"VideoEncoders": {
  "x264": {...},
  "x265": {...}
}
```

As a result, Emby always transcodes using:

```text
libx264
```

instead of Raspberry Pi hardware encoding through:

```text
h264_v4l2m2m
```

However, manual tests performed inside the exact same container successfully use the Raspberry Pi hardware encoder.

---

## Hardware Devices Visible Inside Container

### Video Devices

```bash
ls -l /dev/video*
```

Output:

```text
crw-rw---- 1 root 44 81,2   /dev/video10
crw-rw---- 1 root 44 81,4   /dev/video11
crw-rw---- 1 root 44 81,9   /dev/video12
crw-rw---- 1 root 44 81,1   /dev/video13
crw-rw---- 1 root 44 81,3   /dev/video14
crw-rw---- 1 root 44 81,5   /dev/video15
crw-rw---- 1 root 44 81,6   /dev/video16
crw-rw---- 1 root 44 81,12  /dev/video18
crw-rw---- 1 root 44 81,0   /dev/video19
crw-rw---- 1 root 44 81,7   /dev/video20
crw-rw---- 1 root 44 81,8   /dev/video21
crw-rw---- 1 root 44 81,10  /dev/video22
crw-rw---- 1 root 44 81,11  /dev/video23
crw-rw---- 1 root 44 81,13  /dev/video31
```

### DRM Devices

```bash
ls -l /dev/dri
```

Output:

```text
card0
card1
renderD128
```

### Permissions

```bash
id
```

Output:

```text
uid=0(root)
gid=0(root)
groups=0(root),10(wheel),28(video)
```

---

## Manual FFmpeg Test #1

Executed inside the Emby container using Emby's bundled FFmpeg:

```bash
/bin/ffmpeg \
-i "/mnt/multimedia/series/Series/The Big Bang Theory/Season 2/The Big Bang Theory - s02e05.mkv" \
-c:v h264_v4l2m2m \
-f null -
```

Relevant output:

```text
[h264_v4l2m2m @ 0x19a68b70] Using device /dev/video11
[h264_v4l2m2m @ 0x19a68b70] driver 'bcm2835-codec' on card 'bcm2835-codec-encode' in mplane mode
[h264_v4l2m2m @ 0x19a68b70] requesting formats: output=YU12 capture=H264
```

Transcoding proceeds successfully.

---

## Manual FFmpeg Test #2

Synthetic source test:

```bash
/bin/ffmpeg \
-f lavfi \
-i testsrc=size=1280x720:rate=30 \
-t 20 \
-c:v h264_v4l2m2m \
-f null -
```

Relevant output:

```text
[h264_v4l2m2m @ 0x24c8f020] Using device /dev/video11
[h264_v4l2m2m @ 0x24c8f020] driver 'bcm2835-codec' on card 'bcm2835-codec-encode'
```

Encoding completes successfully.

---

## Hardware Detection Results

The generated `hardware_detection-*.txt` files show:

```json
"VideoDecoders": {}
```

and only software encoders:

```json
"VideoEncoders": {
  "x264": {
    "IsHardwareCodec": false
  },
  "x265": {
    "IsHardwareCodec": false
  }
}
```

No V4L2M2M encoders or decoders are detected.

---

## Actual FFmpeg Command Used By Emby

While playing content that requires transcoding:

```bash
ps auxww | grep ffmpeg
```

shows:

```bash
/bin/ffmpeg \
...
-c:v:0 libx264
...
```

Full relevant section:

```bash
-map [f1_out0]
-c:v:0 libx264
-preset:v:0 veryfast
-profile:v:0 high
-crf:v:0 23
```

Emby never attempts to use:

```text
h264_v4l2m2m
```

even though the encoder works when manually invoked.

---

## Additional Observation

An attempt to use DRM hardware acceleration:

```bash
/bin/ffmpeg \
-hwaccel drm \
-i input.mkv \
-c:v h264_v4l2m2m \
-f null -
```

fails with:

```text
Device creation failed: -14
No device available for decoder: device type drm needed for codec h264
```

However, encoding works correctly when using V4L2M2M directly without DRM hardware decoding.

This suggests the encoder itself is functional and accessible.

---

## Expected Behavior

Emby should detect Raspberry Pi V4L2M2M hardware codecs and offer/use hardware transcoding.

---

## Actual Behavior

Hardware detection reports only software codecs and all transcoding falls back to libx264.

---

## Question

Is Raspberry Pi 4 hardware transcoding through V4L2M2M expected to be supported in Emby Server 4.9.x on ARM64 Docker?

If so:

1. Is there a way to force hardware codec detection?
2. Is additional logging available for the Hardware Detection process?
3. Is V4L2M2M currently supported by Hardware Detection on Raspberry Pi OS / Ubuntu ARM64?

Thank you.

hardware_detection-63916570464.txt

[Abobader 3501]

Hello lugaidvii,

** This is an auto reply **

Please wait for someone from staff support or our members to reply to you.

It's recommended to provide more info, as it explain in this thread:

Thank you.

Emby Team