CRAS = ChromeOS Audio Server Directories src/server - the source for the sound server src/libcras - client library for interacting with cras src/common - files common to both the server and library src/tests - tests for cras and libcras Building from source: ./git_prepare.sh ./configure make sudo make install --------------------- Configuration: --------------------- Device Blacklisting: -------------------- Blacklist of certain USB output device(s) is possible by modifying the config file /etc/cras/device_blacklist. The format of this file is as follows: [USB_Outputs] ___ = 1 Where vendor_id and product id are the USB identifiers for the card to blacklist. The checksum is the output of "cksum" command applied to the sysfs "descriptors" file of the device. The device index specifies the index of the output device in the card to blacklist. This is a bool parameter, so '= 1' enables the option. Example, blacklisting the non-functional output device reported by the C-Media based CAD-u1 mic: [USB_Outputs] 0d8c_0008_00000000_0 = 1 Card Configuration: ------------------- There can be a config file for each sound alsa card on the system. This file lives in /etc/cras/. The file should be named with the card name returned by ALSA, the string in the second set of '[]' in the aplay -l output. The ini file has the following format. [] ; Name of the mixer control for this output. = output-node-name can be speficied in a few ways to link with the real node: UCM device name - The name string following the SectionDevice label in UCM config, i.e. HiFi.conf Jack name - Name of the mixer control for mixer jack, or the gpio jack name listed by 'evtest' command. Mixer control name - e.g. "Headphone" or "Speaker", listed by 'amixer scontrols' command. Note that an output node matches to the output-node-name label in card config by priorty ordered above. For example if a node has UCM device, it will first search the config file for the UCM device name. When not found, jack name will be used for searching, and lastly the mixer output control name. config-option can be the following: volume_curve - The type of volume curve, "simple_step" or "explicit". Options valid and mandatory when volume_curve = simple_step: max_volume - The maximum volume for this output specified in dBFS * 100. volume_step - Number of dB per volume 'tick' specified in dBFS * 100. Options valid and mandatory when volume_curve = explicit: dB_at_N - The value in dB*100 that should be used for the volume at step "N". There must be one of these for each setting from N=0 to 100 inclusive. Example: This example configures the Headphones to have a max volume of -3dBFS with a step size of 0.75dBFS and the Speaker to have the curve specified by the steps given, which is a 1dBFS per step curve from max = +0.5dBFS to min = -99.5dBFS (volume step 10 is -89.5dBFS). [Headphone] volume_curve = simple_step volume_step = 75 max_volume = -300 [Speaker] volume_curve = explicit dB_at_0 = -9950 dB_at_1 = -9850 dB_at_2 = -9750 dB_at_3 = -9650 dB_at_4 = -9550 dB_at_5 = -9450 dB_at_6 = -9350 dB_at_7 = -9250 dB_at_8 = -9150 dB_at_9 = -9050 dB_at_10 = -8950 dB_at_11 = -8850 dB_at_12 = -8750 dB_at_13 = -8650 dB_at_14 = -8550 dB_at_15 = -8450 dB_at_16 = -8350 dB_at_17 = -8250 dB_at_18 = -8150 dB_at_19 = -8050 dB_at_20 = -7950 dB_at_21 = -7850 dB_at_22 = -7750 dB_at_23 = -7650 dB_at_24 = -7550 dB_at_25 = -7450 dB_at_26 = -7350 dB_at_27 = -7250 dB_at_28 = -7150 dB_at_29 = -7050 dB_at_30 = -6950 dB_at_31 = -6850 dB_at_32 = -6750 dB_at_33 = -6650 dB_at_34 = -6550 dB_at_35 = -6450 dB_at_36 = -6350 dB_at_37 = -6250 dB_at_38 = -6150 dB_at_39 = -6050 dB_at_40 = -5950 dB_at_41 = -5850 dB_at_42 = -5750 dB_at_43 = -5650 dB_at_44 = -5550 dB_at_45 = -5450 dB_at_46 = -5350 dB_at_47 = -5250 dB_at_48 = -5150 dB_at_49 = -5050 dB_at_50 = -4950 dB_at_51 = -4850 dB_at_52 = -4750 dB_at_53 = -4650 dB_at_54 = -4550 dB_at_55 = -4450 dB_at_56 = -4350 dB_at_57 = -4250 dB_at_58 = -4150 dB_at_59 = -4050 dB_at_60 = -3950 dB_at_61 = -3850 dB_at_62 = -3750 dB_at_63 = -3650 dB_at_64 = -3550 dB_at_65 = -3450 dB_at_66 = -3350 dB_at_67 = -3250 dB_at_68 = -3150 dB_at_69 = -3050 dB_at_70 = -2950 dB_at_71 = -2850 dB_at_72 = -2750 dB_at_73 = -2650 dB_at_74 = -2550 dB_at_75 = -2450 dB_at_76 = -2350 dB_at_77 = -2250 dB_at_78 = -2150 dB_at_79 = -2050 dB_at_80 = -1950 dB_at_81 = -1850 dB_at_82 = -1750 dB_at_83 = -1650 dB_at_84 = -1550 dB_at_85 = -1450 dB_at_86 = -1350 dB_at_87 = -1250 dB_at_88 = -1150 dB_at_89 = -1050 dB_at_90 = -950 dB_at_91 = -850 dB_at_92 = -750 dB_at_93 = -650 dB_at_94 = -550 dB_at_95 = -450 dB_at_96 = -350 dB_at_97 = -250 dB_at_98 = -150 dB_at_99 = -50 dB_at_100 = 50