From 90e7bf17d7b535c66887414baa5c2187822117c3 Mon Sep 17 00:00:00 2001 From: Andre Noll Date: Sun, 15 Mar 2009 17:35:37 +0100 Subject: [PATCH 1/1] alsa: Split alsa_open(). Only perform what is absolutely necessary in alsa_open(). Call the real alsa initialization from alsa_post_select(), when we actually have audio data available to start streaming. This should get rid of the sound artefacts that happen sometimes at the beginning of the stream. --- alsa_write.c | 77 +++++++++++++++++++++++++++++----------------------- 1 file changed, 43 insertions(+), 34 deletions(-) diff --git a/alsa_write.c b/alsa_write.c index dfd2421d..f63b7a5e 100644 --- a/alsa_write.c +++ b/alsa_write.c @@ -1,5 +1,5 @@ /* - * Copyright (C) 2005-2008 Andre Noll + * Copyright (C) 2005-2009 Andre Noll * * Licensed under the GPL v2. For licencing details see COPYING. */ @@ -51,33 +51,16 @@ struct private_alsa_write_data { unsigned channels; }; -/* - * open and prepare the PCM handle for writing - * - * Install PCM software and hardware configuration. Exit on errors. - */ -static int alsa_open(struct writer_node *w) +/* Install PCM software and hardware configuration. */ +static int alsa_init(struct private_alsa_write_data *pad, + struct alsa_write_args_info *conf) { snd_pcm_hw_params_t *hwparams; snd_pcm_sw_params_t *swparams; snd_pcm_uframes_t buffer_size, start_threshold, stop_threshold; - int err; snd_pcm_uframes_t period_size; - struct private_alsa_write_data *pad = para_calloc(sizeof(struct - private_alsa_write_data)); - struct alsa_write_args_info *conf = w->conf; - struct writer_node_group *wng = w->wng; + int err; - if (!conf->samplerate_given && wng->samplerate) - pad->samplerate = *wng->samplerate; - else - pad->samplerate = conf->samplerate_arg; - if (!conf->channels_given && wng->channels) - pad->channels = *wng->channels; - else - pad->channels = conf->channels_arg; - PARA_INFO_LOG("%d channel(s), %dHz\n", pad->channels, pad->samplerate); - w->private_data = pad; err = snd_pcm_open(&pad->handle, conf->device_arg, SND_PCM_STREAM_PLAYBACK, SND_PCM_NONBLOCK); if (err < 0) @@ -133,7 +116,27 @@ static int alsa_open(struct writer_node *w) PARA_INFO_LOG("bytes per frame: %zu\n", pad->bytes_per_frame); if (snd_pcm_nonblock(pad->handle, 1)) PARA_ERROR_LOG("failed to set nonblock mode\n"); - tv_add(now, &(struct timeval ){0, 100 * 1000}, &pad->next_chunk); + return 1; +} + +/* Open an instance of the alsa writer. */ +static int alsa_open(struct writer_node *wn) +{ + struct alsa_write_args_info *conf = wn->conf; + struct writer_node_group *wng = wn->wng; + struct private_alsa_write_data *pad = para_calloc(sizeof(*pad)); + + wn->private_data = pad; + if (!conf->samplerate_given && wng->samplerate) + pad->samplerate = *wng->samplerate; + else + pad->samplerate = conf->samplerate_arg; + if (!conf->channels_given && wng->channels) + pad->channels = *wng->channels; + else + pad->channels = conf->channels_arg; + PARA_INFO_LOG("%d channel(s), %dHz\n", pad->channels, pad->samplerate); + tv_add(now, &(struct timeval){0, 100 * 1000}, &pad->next_chunk); return 1; } @@ -143,7 +146,7 @@ static int alsa_write_pre_select(struct sched *s, struct writer_node *wn) struct writer_node_group *wng = wn->wng; struct timeval diff; - if (*wng->loaded < pad->bytes_per_frame) + if (!*wng->loaded) return 1; if (tv_diff(now, &pad->next_chunk, &diff) < 0) { if (tv_diff(&s->timeout, &diff, NULL) > 0) @@ -153,7 +156,6 @@ static int alsa_write_pre_select(struct sched *s, struct writer_node *wn) s->timeout.tv_usec = 1; } return 1; -// PARA_INFO_LOG("timeout: %lu\n", tv2ms(&s->timeout)); } static int alsa_write_post_select(__a_unused struct sched *s, @@ -161,19 +163,21 @@ static int alsa_write_post_select(__a_unused struct sched *s, { struct private_alsa_write_data *pad = wn->private_data; struct writer_node_group *wng = wn->wng; - size_t frames = (*wng->loaded - wn->written) / pad->bytes_per_frame; - snd_pcm_sframes_t ret; + size_t frames, bytes = *wng->loaded - wn->written; unsigned char *data = (unsigned char*)wng->buf + wn->written; struct timeval tv; + snd_pcm_sframes_t ret; -// PARA_INFO_LOG("%zd frames\n", frames); - if (!frames) { - if (*wng->input_error) - wn->written = *wng->loaded; - return 1; - } + if (!bytes) /* no data available */ + goto out; if (tv_diff(now, &pad->next_chunk, NULL) < 0) - return 1; + goto out; + if (!pad->handle) { + int err = alsa_init(pad, wn->conf); + if (err < 0) + return err; + } + frames = bytes / pad->bytes_per_frame; ret = snd_pcm_writei(pad->handle, data, frames); if (ret == -EPIPE) { PARA_WARNING_LOG("EPIPE\n"); @@ -195,6 +199,11 @@ static int alsa_write_post_select(__a_unused struct sched *s, ms2tv(pad->buffer_time / pad->bytes_per_frame / 1000, &tv); tv_add(now, &tv, &pad->next_chunk); } +out: + if (*wng->input_error < 0) { + wn->written = *wng->loaded; + return *wng->input_error; + } return 1; } -- 2.30.2