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David's questions

Martin Hope
David
Asked: 2018-02-28 05:58:58 +0800 CST
  • 8

我今天遇到了一些奇怪的行为：

#!/bin/bash
set -ex
export a=$(cat foo)
echo "It's a living thing"
b=$(cat foo)
echo "This won't make it"

cat foo即使foo不存在，这也不会停止。但是没有导出，它会失败。为什么？

bash shell
Martin Hope
David
Asked: 2018-01-14 12:02:31 +0800 CST
  • 3

我有一块GIGABYTE GA-H170N-WIFI主板，我想将它用作家庭音响系统的基础。它有两个HDMI输出和5.1模拟音频输出。

问题是，如何知道声卡/子系统支持多少个独立音频通道？我真的可以每个 HDMI 输出有 8 个独立的音频通道，外加 6 个模拟通道（更不用说 S/PDIF 输出上多达 8 个通道）同时运行，发送不同的信号吗？此外，是否可以说服 PulseAudio “拆分” HDMI 音频通道并将它们作为 8 个独立的接收器提供？

谢谢！

更新：我的 /proc/asound/card0/codec#2

Codec: Intel Skylake HDMI
Address: 2
AFG Function Id: 0x1 (unsol 0)
Vendor Id: 0x80862809
Subsystem Id: 0x80860101
Revision Id: 0x100000
No Modem Function Group found
Default PCM:
    rates [0x0]:
    bits [0x0]:
    formats [0x0]:
Default Amp-In caps: N/A
Default Amp-Out caps: N/A
State of AFG node 0x01:
  Power states:  D0 D3 CLKSTOP EPSS
  Power: setting=D0, actual=D0, Clock-stop-OK
GPIO: io=0, o=0, i=0, unsolicited=0, wake=0
Node 0x02 [Audio Output] wcaps 0x6611: 8-Channels Digital
  Converter: stream=0, channel=0
  Digital: Enabled KAE
  Digital category: 0x0
  IEC Coding Type: 0x0
  PCM:
    rates [0x7f0]: 32000 44100 48000 88200 96000 176400 192000
    bits [0x1a]: 16 24 32
    formats [0x5]: PCM AC3
  Power states:  D0 D3 EPSS
  Power: setting=D0, actual=D0
Node 0x03 [Audio Output] wcaps 0x6611: 8-Channels Digital
  Converter: stream=0, channel=0
  Digital: Enabled KAE
  Digital category: 0x0
  IEC Coding Type: 0x0
  PCM:
    rates [0x7f0]: 32000 44100 48000 88200 96000 176400 192000
    bits [0x1a]: 16 24 32
    formats [0x5]: PCM AC3
  Power states:  D0 D3 EPSS
  Power: setting=D0, actual=D0
Node 0x04 [Audio Output] wcaps 0x6611: 8-Channels Digital
  Converter: stream=0, channel=0
  Digital: Enabled KAE
  Digital category: 0x0
  IEC Coding Type: 0x0
  PCM:
    rates [0x7f0]: 32000 44100 48000 88200 96000 176400 192000
    bits [0x1a]: 16 24 32
    formats [0x5]: PCM AC3
  Power states:  D0 D3 EPSS
  Power: setting=D0, actual=D0
Node 0x05 [Pin Complex] wcaps 0x40778d: 8-Channels Digital Amp-Out CP
  Amp-Out caps: ofs=0x00, nsteps=0x00, stepsize=0x00, mute=1
  Amp-Out vals:  [0x00 0x00]
  Pincap 0x0b000094: OUT Detect HBR HDMI DP
  Pin Default 0x18560010: [Jack] Digital Out at Int HDMI
    Conn = Digital, Color = Unknown
    DefAssociation = 0x1, Sequence = 0x0
  Pin-ctls: 0x40: OUT
  Unsolicited: tag=00, enabled=0
  Power states:  D0 D3 EPSS
  Power: setting=D0, actual=D0
  Devices: 0
  Connection: 3
     0x02* 0x03 0x04
Node 0x06 [Pin Complex] wcaps 0x40778d: 8-Channels Digital Amp-Out CP
  Amp-Out caps: ofs=0x00, nsteps=0x00, stepsize=0x00, mute=1
  Amp-Out vals:  [0x00 0x00]
  Pincap 0x0b000094: OUT Detect HBR HDMI DP
  Pin Default 0x18560010: [Jack] Digital Out at Int HDMI
    Conn = Digital, Color = Unknown
    DefAssociation = 0x1, Sequence = 0x0
  Pin-ctls: 0x00:
  Unsolicited: tag=00, enabled=0
  Power states:  D0 D3 EPSS
  Power: setting=D0, actual=D0
  Devices: 0
  Connection: 0
  In-driver Connection: 3
     0x02 0x03 0x04
Node 0x07 [Pin Complex] wcaps 0x40778d: 8-Channels Digital Amp-Out CP
  Amp-Out caps: ofs=0x00, nsteps=0x00, stepsize=0x00, mute=1
  Amp-Out vals:  [0x00 0x00]
  Pincap 0x0b000094: OUT Detect HBR HDMI DP
  Pin Default 0x18560010: [Jack] Digital Out at Int HDMI
    Conn = Digital, Color = Unknown
    DefAssociation = 0x1, Sequence = 0x0
  Pin-ctls: 0x00:
  Unsolicited: tag=00, enabled=0
  Power states:  D0 D3 EPSS
  Power: setting=D0, actual=D0
  Devices: 0
  Connection: 0
  In-driver Connection: 3
     0x02 0x03 0x04
Node 0x08 [Vendor Defined Widget] wcaps 0xf00000: Mono
audio pulseaudio