From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0B0F9C2D0DB for ; Thu, 30 Jan 2020 23:28:56 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id CAC2820708 for ; Thu, 30 Jan 2020 23:28:55 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CAC2820708 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=tum.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:40960 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ixJF0-0004Te-WD for qemu-devel@archiver.kernel.org; Thu, 30 Jan 2020 18:28:55 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:40481) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ixHwS-00019b-GW for qemu-devel@nongnu.org; Thu, 30 Jan 2020 17:05:41 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ixHwR-00046v-1Y for qemu-devel@nongnu.org; Thu, 30 Jan 2020 17:05:40 -0500 Received: from indium.canonical.com ([91.189.90.7]:35572) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1ixHwQ-00045S-ST for qemu-devel@nongnu.org; Thu, 30 Jan 2020 17:05:38 -0500 Received: from loganberry.canonical.com ([91.189.90.37]) by indium.canonical.com with esmtp (Exim 4.86_2 #2 (Debian)) id 1ixHwP-0006rE-F9 for ; Thu, 30 Jan 2020 22:05:37 +0000 Received: from loganberry.canonical.com (localhost [127.0.0.1]) by loganberry.canonical.com (Postfix) with ESMTP id 6AE622E80C0 for ; Thu, 30 Jan 2020 22:05:37 +0000 (UTC) MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Date: Thu, 30 Jan 2020 21:59:21 -0000 From: Noah Bergbauer To: qemu-devel@nongnu.org X-Launchpad-Notification-Type: bug X-Launchpad-Bug: product=qemu; status=New; importance=Undecided; assignee=None; X-Launchpad-Bug-Information-Type: Public X-Launchpad-Bug-Private: no X-Launchpad-Bug-Security-Vulnerability: no X-Launchpad-Bug-Commenters: noah-bergbauer X-Launchpad-Bug-Reporter: Noah Bergbauer (noah-bergbauer) X-Launchpad-Bug-Modifier: Noah Bergbauer (noah-bergbauer) Message-Id: <158042156192.19296.13362308580628501069.malonedeb@gac.canonical.com> Subject: [Bug 1861458] [NEW] Clock drift issue with -soundhw hda X-Launchpad-Message-Rationale: Subscriber (QEMU) @qemu-devel-ml X-Launchpad-Message-For: qemu-devel-ml Precedence: bulk X-Generated-By: Launchpad (canonical.com); Revision="0a62c17273454a1313f81a74a2198ec30b44c7b6"; Instance="production-secrets-lazr.conf" X-Launchpad-Hash: b77550c681cfc6d388ecf16cda8ce5f67b8f5446 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 91.189.90.7 X-Mailman-Approved-At: Thu, 30 Jan 2020 18:27:55 -0500 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Bug 1861458 <1861458@bugs.launchpad.net> Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Public bug reported: Here's the scenario: I'm working on code for loopback audio recording (i.e. recording what you're hearing) using WASAPI on Windows. As I usually develop on Linux, I'm using qemu to test this on a Windows 10 VM. The heart of WASAPI audio recording is the IAudioCaptureClient::GetBuffer function (https://docs.microsoft.com/en- us/windows/win32/api/audioclient/nf-audioclient-iaudiocaptureclient- getbuffer). Among other things, this function produces a timestamp for when the audio buffer it returned is supposed to be played. When the audio device in question is the qemu hda device, this timestamp is wrong. There is a clock drift error (I measured it to be about 0.1%, i.e. 1ms drift every second =3D a full second after 16 minutes) that causes the audio clock to advance faster than the system clock. Paradoxically, this does not affect audio playback through qemu at all, no delay there. Only the timestamps returned to recording applications are completely bogus. Unfortunately I'm not intimately familiar with the inner workings of Intel HD Audio. All I can tell you is that this timestamp is supposedly obtained directly from the hardware (which would be qemu in this case), which is also why e.g. chromium implements a workaround for buggy hardware that returns incorrect timestamps. Here are the relevant parts of my command line (version 4.2.0): -enable-kvm -machine pc-q35-3.1,kernel-irqchip=3Don -cpu host,kvm=3Doff,hv_= time,hv_relaxed,hv_vapic,hv_spinlocks=3D0x1fff,hv_vendor_id=3DNvidiaFuckU -= rtc base=3Dlocaltime -nodefaults -soundhw hda Just wanted to let you know about this because it took me three days of utter confusion and frustration to figure this out. ** Affects: qemu Importance: Undecided Status: New -- = You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1861458 Title: Clock drift issue with -soundhw hda Status in QEMU: New Bug description: Here's the scenario: I'm working on code for loopback audio recording (i.e. recording what you're hearing) using WASAPI on Windows. As I usually develop on Linux, I'm using qemu to test this on a Windows 10 VM. The heart of WASAPI audio recording is the IAudioCaptureClient::GetBuffer function (https://docs.microsoft.com /en-us/windows/win32/api/audioclient/nf-audioclient- iaudiocaptureclient-getbuffer). Among other things, this function produces a timestamp for when the audio buffer it returned is supposed to be played. When the audio device in question is the qemu hda device, this timestamp is wrong. There is a clock drift error (I measured it to be about 0.1%, i.e. 1ms drift every second =3D a full second after 16 minutes) that causes the audio clock to advance faster than the system clock. Paradoxically, this does not affect audio playback through qemu at all, no delay there. Only the timestamps returned to recording applications are completely bogus. Unfortunately I'm not intimately familiar with the inner workings of Intel HD Audio. All I can tell you is that this timestamp is supposedly obtained directly from the hardware (which would be qemu in this case), which is also why e.g. chromium implements a workaround for buggy hardware that returns incorrect timestamps. Here are the relevant parts of my command line (version 4.2.0): -enable-kvm -machine pc-q35-3.1,kernel-irqchip=3Don -cpu host,kvm=3Doff,h= v_time,hv_relaxed,hv_vapic,hv_spinlocks=3D0x1fff,hv_vendor_id=3DNvidiaFuckU= -rtc base=3Dlocaltime -nodefaults -soundhw hda Just wanted to let you know about this because it took me three days of utter confusion and frustration to figure this out. To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1861458/+subscriptions