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meyer9

Member

Registered: 2020-03-31

Posts: 3

Webcam on Razer Blade 2017 not working

I'm having issues with my Razer Blade 2017 webcam. It doesn't display anything or freezes after 0.1 seconds.

I found this thread from 2014 having issues with the same webcam, but it's unresolved: https://www.spinics.net/lists/linux-media/msg73476.html

I did some digging into the uvcvideo kernel module and found that it's reporting an incorrect dwMaxVideoFrameSize.

[   80.490256] uvcvideo: Frame complete (FID bit toggled).
[   80.490262] uvcvideo: frame 2080 stats: 0/0/1 packets, 0/0/0 pts (!early !initial), 0/1 scr, last pts/stc/sof 0/2069725020/32605
[   80.490264] uvcvideo: Marking buffer as bad (error bit set).
[   80.490606] uvcvideo: Frame complete (EOF found).
[   80.490942] uvcvideo: Marking buffer as bad (error bit set).
[   80.490947] uvcvideo: Dropping payload (out of sync).
[   80.492920] uvcvideo: Marking buffer as bad (error bit set).

After more investigation, I found this line at the end of uvc_video_decode_bulk that was causing the problem:

if (buf->bytesused == stream->queue.buf_used ||
  stream->bulk.payload_size == stream->bulk.max_payload_size) {
   // assume end of frame
}

I also ran a USBMon on the webcam and decoded it using the python script in the thread linked above. This yielded the following setup URB:

bmHint                         0x01
bFormatIndex                      1
bFrameIndex                       1
dwFrameInterval              333333
wKeyFrameRate                     0
wPFrameRate                       0
wCompQuality                      0
wCompWindowSize                   0
wDelay                           32
dwMaxVideoFrameSize          614400
dwMaxPayloadTransferSize     119296

I also calculated the size of a video frame by adding up the lengths of each URB sent. So, after this, it sends the UVC header, which looks correct:

0c8d6018 3bbcfa9b    .`.;¼ú›
3cbc3304 727a7082    <¼3.rzp‚
717c717d 6f7e7089    q|q}o~p‰
6e816f89 6e826e88    no‰n‚nˆ

In total sends 37 16384 byte URBs and one 8264 byte URB or 614472 bytes total (greater than the 614400 specified in the URB by 72 bytes). I tried removing the second condition from the if statement above and making it consider the end of frame based on finding a URB with size less than dwMaxVideoFrameSize and that seemed to change the problem at least.

Now, it was overflowing the V4L plane size which was set to 614400. It seems this is specified somewhere in uvc_queue_setup:

struct uvc_video_queue *queue = vb2_get_drv_priv(vq);
struct uvc_streaming *stream;
unsigned int size;
switch (vq->type) {
case V4L2_BUF_TYPE_META_CAPTURE:
	size = UVC_METADATA_BUF_SIZE;
	break;

default:
	stream = uvc_queue_to_stream(queue);
	size = stream->ctrl.dwMaxVideoFrameSize; // + 72
	break;
}

I'm not really sure where to go from here. It's not always 72 bytes over either. I've found that if I switch the resolution/format, it can be a different number.

meyer9

Member

Registered: 2020-03-31

Posts: 3

Re: Webcam on Razer Blade 2017 not working

Submitted a kernel patch to fix the issue:

https://lore.kernel.org/patchwork/patch/1219476/

velocity303

Member

Registered: 2014-11-03

Posts: 1

Re: Webcam on Razer Blade 2017 not working

Thanks so much for that fix meyer9!

I have an older Razer Blade 2014 that always had a broken webcam on linux. I just recompiled my kernel in PopOS using your patch and it fixed that issue for me. Thanks so much for submitting this upstream! I hope it gets merged in soon.

meyer9

Member

Registered: 2020-03-31

Posts: 3

Re: Webcam on Razer Blade 2017 not working

Hey velociy303, no problem!

Be a little careful with that patch. I have experienced some freezes with it and I'm working on fixing, although they haven't happened except under certain circumstances.