RE: [RFC] Fix interrupted recording with Hauppauge HD-PVR

["Ryley Angus" <ryleyjangus@gmail.com>]

Thanks Hans for getting back to me.

I've been trying out your patch and I found the device wasn't actually
restarting the streaming/recording properly after a channel 
change. I changed "msecs_to_jiffies(500))" to "msecs_to_jiffies(1000))" and
had the same issue, but "msecs_to_jiffies(2000))" 
seems to be working well. I'll let it keep going for a few more hours, but
at the moment it seems to be working well. The recordings
can be ended without anything hanging, and turning off the device ends the
recording properly (mine neglected this occurrence).

I'll let you know if I have any more issues,

ryley

-----Original Message-----
From: Hans Verkuil [mailto:hverkuil@xs4all.nl] 
Sent: Tuesday, April 08, 2014 12:07 AM
To: Ryley Angus; linux-media@vger.kernel.org
Subject: Re: [RFC] Fix interrupted recording with Hauppauge HD-PVR

Hi Ryley,

Thank you for the patch. Your analysis seems sound. The patch is actually
not bad for a first attempt, but I did it a bit differently.

Can you test my patch?

Regards,

	Hans

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>

diff --git a/drivers/media/usb/hdpvr/hdpvr-video.c
b/drivers/media/usb/hdpvr/hdpvr-video.c
index 0500c417..a61373e 100644
--- a/drivers/media/usb/hdpvr/hdpvr-video.c
+++ b/drivers/media/usb/hdpvr/hdpvr-video.c
@@ -454,6 +454,8 @@ static ssize_t hdpvr_read(struct file *file, char __user
*buffer, size_t count,
 
 		if (buf->status != BUFSTAT_READY &&
 		    dev->status != STATUS_DISCONNECTED) {
+			int err;
+
 			/* return nonblocking */
 			if (file->f_flags & O_NONBLOCK) {
 				if (!ret)
@@ -461,11 +463,23 @@ static ssize_t hdpvr_read(struct file *file, char
__user *buffer, size_t count,
 				goto err;
 			}
 
-			if (wait_event_interruptible(dev->wait_data,
-					      buf->status == BUFSTAT_READY))
{
-				ret = -ERESTARTSYS;
+			err =
wait_event_interruptible_timeout(dev->wait_data,
+					      buf->status == BUFSTAT_READY,
+					      msecs_to_jiffies(500));
+			if (err < 0) {
+				ret = err;
 				goto err;
 			}
+			if (!err) {
+				v4l2_dbg(MSG_INFO, hdpvr_debug,
&dev->v4l2_dev,
+					"timeout: restart streaming\n");
+				hdpvr_stop_streaming(dev);
+				err = hdpvr_start_streaming(dev);
+				if (err) {
+					ret = err;
+					goto err;
+				}
+			}
 		}
 
 		if (buf->status != BUFSTAT_READY)


On 04/07/2014 02:04 AM, Ryley Angus wrote:
> (Sorry in advance for probably breaking a few conventions of the 
> mailing lists. First time using one so please let me know what I'm 
> doing wrong)
> 
> I'm writing this because of an issue I had with my Hauppauge HD-PVR.
> I record from my satellite set top box using component video and 
> optical audio input. I basically use "cat /dev/video0 > ~/video.ts"
> or use dd. The box is set to output audio as AC-3 over optical, but 
> most channels are actually output as stereo PCM. When the channel is 
> changed between a PCM channel and (typically to a movie channel) to a 
> channel utilising AC-3, the HD-PVR stops the recording as the set top 
> box momentarily outputs no audio. Changing between PCM channels 
> doesn't cause any issues.
> 
> My main problem was that when this happens, cat/dd doesn't actually 
> exit. When going through the hdpvr driver source and the dmesg output, 
> I found the hdpvr driver wasn't actually shutting down the device 
> properly until I manually killed cat/dd.
> 
> I've seen references to this issue being a hardware issue from as far 
> back as 2010:
> http://forums.gbpvr.com/showthread.php?46429-HD-PVR-drops-recording-on
> -channel-change-Hauppauge-says-too-bad
> .
> 
> I tracked my issue to the file "hdpvr-video.c". Specifically, "if 
> (wait_event_interruptible(dev->wait_data, buf->status =
> BUFSTAT_READY)) {" (line ~450). The device seems to get stuck waiting 
> for the buffer to become ready. But as far as I can tell, when the 
> channel is changed between a PCM and AC-3 broadcast the buffer status 
> will never actually become ready.
> 
> I haven't really ever done much coding, but I wrote a really nasty 
> patch for this which tracks the devices buffer status and stops/starts 
> the devices recording when the buffer is not ready for a period of 
> time. In my limited testing it has worked perfectly, no output is 
> overwritten, the output is in sync and the recording changes perfectly 
> between stereo AC-3 (PCM input is encoded to AC-3 by the hardware) and 
> 5.1 AC-3 no matter how frequently I change the channels back and 
> forth. All changes are transparent to cat/dd and neither exit 
> prematurely. Manually killing cat/dd seems to properly shut down the 
> device. There is a half-second glitch in the resultant where the 
> recording restarts, but this amounts to less than a second of lost 
> footage during the change and compared to having the device hang, I 
> can live with it. I haven't had the device restart recording when it 
> shouldn't have.
> 
> So considering my code is really messy, I'd love it if someone could 
> make some suggestions to make the code better and make sure I don't 
> have too many logic errors. I don't really know too much about kernel 
> coding practices either. And if anyone who's experienced my issue 
> could try out my change and let me know that'd be great. You will have 
> to run "v4l2-ctl --verbose -d /dev/video0 -c audio_encoding=4"
> to ensure the 5.1 AC-3 is captured properly (AAC capture of 5.1 
> sources doesn't seem possible) and "v4l2-ctl --verbose -d $MPEG4_IN 
> --set-audio-input=2" to capture from the optical input.
> Thanks in advance,
> 
> ryley
> 
> 
> --- a/hdpvr-video.c	2014-04-07 09:34:31.000000000 +1000
> +++ b/hdpvr-video.c	2014-04-07 09:37:44.000000000 +1000
> @@ -453,11 +453,17 @@
>  					ret = -EAGAIN;
>  				goto err;
>  			}
> -
> -			if (wait_event_interruptible(dev->wait_data,
> -					      buf->status == BUFSTAT_READY))
{
> -				ret = -ERESTARTSYS;
> -				goto err;
> +			int counter=0;
> +			while (buf->status != BUFSTAT_READY) {
> +				counter++;
> +				msleep(20);
> +				if (counter == 30) {
> +					v4l2_dbg(MSG_INFO, hdpvr_debug,
&dev->v4l2_dev,
> +                                                "limit hit, counter is
%d, buf status is %d\n", counter, buf->status);
> +					counter=0;
> +					ret = hdpvr_stop_streaming(dev);
> +					ret = hdpvr_start_streaming(dev);
> +				}
>  			}
>  		}
> 
> 
> 
> 
> 
> 



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