Cc: qemu-devel@nongnu.org
cc Volker Rümelin
==========================================
so I was curious about:
1. why using wpos, rpos which will increasing along the time, which
may overflow in the feature time?
wpos and rpos are 64 bit integers. At a sample rate of 96kHz and with 32
bit stereo audio frames they overflow after 2^63 bytes / (8 bytes/frame
* 96000 frames/s) = 1.2E13 s = 380561.23 years. I don't think you will
notice an overflow.
But you're right anyway. The wanted_rpos and wanted_wpos calculation
overflows quite early. At a sample rate of 44100kHz and with 16 bit
stereo samples the multiplication hda_bytes_per_second(st) * (now -
buft_start) overflows after 2^63 bytes / 176400 bytes/ns = 5,23E13 ns =
14.58 hours.
I don't think your fix below is correct. There are certainly ways to
prevent the overflow without resetting the buffer.
2. how to fix the wanted_wpos or wanted_rpos, I current don't
understand the wanted_pos mean and how it work to optimize the codec
This is a jitter-buffer implementation to decouple the audio backend
updates from the hda device updates. The code splits large >10ms sized
audio packets into 1ms sized audio packets.
With best regards,
Volker
=======================================================================================================
Currently I got Playback and Capture issue
I test Playing and recoding for a very long time, Playback issue is
hard to reproduce, Capture issue is easy to reproduce for recording
about 14 hours
Playback issue current can only be found on qemu 2.11, which I found
the code below (remove some unnecessary)
wanted_wpos overflow, and is always little then the wpos,(current wpos
- rpos = 0) so qemu will no long get data from vm, as a result
static void hda_audio_output_timer(void *opaque)
{
.............
int64_t wanted_wpos = hda_bytes_per_second(st) * (now -
buft_start) ============> overflow here
/ NANOSECONDS_PER_SECOND;
wanted_wpos &= -4; /* IMPORTANT! clip to frames */
if (wanted_wpos <= wpos) {
/* we already received the data */
goto out_timer;
}
}
Capture issue: Just record all the time
(i using qemu 6.0 to test) I add code below to the input callback
function like below, the issue dispear
hda_audio_input_cb
if (wpos - rpos == B_SIZE) {
/* drop buffer, reset timer adjust */
st->rpos = 0;
st->wpos = 0;
st->buft_start = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
error_report("input drop buffer, reset timer adjust\n");
return;
}
