Re: [linux-audio-user] snd-hdsp+cardbus=distortion -- the sagacontinues (cardbus driver=culprit?) UPDATE: 99.9% sure it is the cardbus driver yenta_socket

he pointed out that it's probably a kernel problem ... we don't want you to solve problems of the alsa driver, but we suspect there is a problem with the cardbus bridge... basics: 1.) the card is a combination of 2 devices: a interface device, either a pci or a cardbus card, and a dsp device, either digital or analog audio ... no problems have ever been reported about the pci interface, so it's likely to be a problem with the cardbus interface ... although i have to admit, that there are only 3 reported systems that have the problems, we experience ... but these systems are completely different ones (p4 / amd64, different cardbus bridges) 2.) the dsp device has an internal matrix mixer, that's independant from the computer (this audio data isn't sent to the computer at all) ... in fact it's possible to set the matrix mixer and unplug the dsp device from the computer ... there are three problems, that show the situation: 3.) if we start an audio application that produces interrupts on the hdsp device, some of the audio data that's been transfered to the computer will be copied or mapped to the buffer of the audio data that's been transfered from the computer to the corresponding output. this could either happen - inside the device itself (i doubt that, since the same driver, the same firmware, the same devices are working without and problems on other linux machines or with windows on the same machine) - inside the cardbus bridge - inside the kernel 4.) if we start the audio playback, the audio playback seems to be distorted: one block of samples will be followed by one block of samples of 0 (zero) ... note that these block are not the blocks of data, that are sent to the hdsp during one interrupt. it's usually 32 samples of sound followed by 32 samples of silence, the driver sends blocks of 64 to 8192 during one interrupt depending on user settings... iirc one sample is 24 bit on the other hand the blocks of silence aren't missing, but the alsa layer will adapt, so that it takes twice as long as it should to play back a soundfile (i'm not sure if it's because of the alsa soundfile player or of the driver) 5.) the reason why we (or at least i) think, that it's a problem with the cardbus interface, is because of jack's output ... jack is both an audio connection interface for different softwares and a very good alsa implementation... using jack as super user in realtime mode, it complains about latency problems: delay of xxx usecs exceeds estimated spare time of yyy; restart ... at the default sample rate of 48000 xxx only about 0.06 % bigger than yyy ... on the other hand, i only get this error on sample rates of more than 32000 ... although the sound at 32000 is distorted, as well... other thoughts i had: 6.) the distortion isn't affected by the block size / the number of interrupts ... it is affected by the samplerate ... that's why i think, there are always 32 samples (768 bit) followed by 32 samples of silence (768 bit zero ???) 7.) the problems occured on different cardbus bridges: ENE C1410 (ico / mandrake) o2micro6933 (myself / gentoo) Texas Instruments PCI1250 (timothy / red hat) i don't know what's the reason for the problems, the latency or the mapping problem, or if there is something else that results this problem ... but since it's a software and not a hardware issue (works fine with windows), i'd like to get into it, and at least try to solve it ... but since i'm neiter a kernel hacker nor i have any idea about the hardware internals, i'd need some help from some people, who are able to help me... i don't want some people to solve my problems for me, but i'd appreciate any help of people, who know what's going on inside the computer... cheers ... Tim mailto:TimBlechmann@gmx.de ICQ: 96771783 -- The only people for me are the mad ones, the ones who are mad to live, mad to talk, mad to be saved, desirous of everything at the same time, the ones who never yawn or say a commonplace thing, but burn, burn, burn, like fabulous yellow roman candles exploding like spiders across the stars and in the middle you see the blue centerlight pop and everybody goes "Awww!" Jack Kerouac