From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from pv33p04im-asmtp001.me.com ([17.143.181.10]:55760 "EHLO pv33p04im-asmtp001.me.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933053AbcIFKwI (ORCPT ); Tue, 6 Sep 2016 06:52:08 -0400 Received: from process-dkim-sign-daemon.pv33p04im-asmtp001.me.com by pv33p04im-asmtp001.me.com (Oracle Communications Messaging Server 7.0.5.38.0 64bit (built Feb 26 2016)) id <0OD200000WNZKG00@pv33p04im-asmtp001.me.com> for linux-media@vger.kernel.org; Tue, 06 Sep 2016 10:51:56 +0000 (GMT) Content-type: text/plain; charset=utf-8 MIME-version: 1.0 (Mac OS X Mail 9.3 \(3124\)) Subject: Re: uvcvideo error on second capture from USB device, leading to V4L2_BUF_FLAG_ERROR From: Oliver Collyer In-reply-to: <20160905201935.wpgtrtt7e4bjjylo@zver> Date: Tue, 06 Sep 2016 13:51:51 +0300 Cc: Andrey Utkin Content-transfer-encoding: quoted-printable Message-id: References: <20160904192538.75czuv7c2imru6ds@zver> <20160905201935.wpgtrtt7e4bjjylo@zver> To: linux-media@vger.kernel.org Sender: linux-media-owner@vger.kernel.org List-ID: So today I installed Ubuntu 16.04 on another PC (this one a high spec = machine with a Rampage V Extreme motherboard) and I reproduced exactly = the same errors and trace. Rebooting the same PC back into Windows 10 and using the same USB 3.0 = port, I had no problems capturing using FFmpeg via DirectShow. I could = start and stop the capture repeatedly without any warnings or errors = appearing in FFmpeg (built from the same source). If the hardware is misbehaving, on both these capture devices, then DS = must be handling it better than V4L2. Or there is simply an obscure bug = in V4L2 which only manifests itself with certain devices. Would providing ssh access to the machine be of interest to anyone who = wants to debug this? > On 5 Sep 2016, at 23:19, Andrey Utkin = wrote: >=20 > On Mon, Sep 05, 2016 at 10:43:49PM +0300, Oliver Collyer wrote: >> I do not have any knowledge of uvcvideo and the associated classes = apart from the studying I=E2=80=99ve done the past day or two, but it = seems likely that error -71 and the later setting of V4L2_BUF_FLAG_ERROR = are linked. Also, the fact it only happens in captures after the first = one suggests something isn=E2=80=99t being cleared down or released = properly in uvcvideo/v4l2-core at the end of the first capture. >>=20 >> Let me know what I need to do next to further narrow it down. >=20 > Have tried to reproduce this (with kernel 4.6.0 and fresh build of > ffmpeg) with uvcvideo-driven laptop webcam, and it doesn't happen to = me. > Also -EPROTO in uvcvideo comes from low-level USB stuff, see > drivers/media/usb/uvc/uvc_status.c:127: >=20 > case -EPROTO: /* Device is disconnected (reported by = some > * host controller). */ >=20 > So it seems like hardware misbehaves. To further clairify situation, I > have such question: do the devices work in other operation systems on > the same machine? >=20 > Reviewing your original email mentioning that two different devices > reproduce same problem, which is apparently related to disconnection = in > the middle of USB communication, I came to me that the connected = device > may be underpowered. So, > - try plugging your devices through reliable _active_ USB hub, > - use the most reliable cables you can get, > - plug into USB 3.0 port if available - it should provide more power > than 1.0 and 2.0. > -- > To unsubscribe from this list: send the line "unsubscribe linux-media" = in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html