Add ALSA support in libavdevice.

Patch by Nicolas George: name surname normalesup org
Original thread: [FFmpeg-devel] [PATCH] ALSA for libavdevice
Date: 12/09/2008 07:17 PM

Originally committed as revision 16800 to svn://svn.ffmpeg.org/ffmpeg/trunk

1 files changed, 186 insertions, 0 deletions

diff --git a/libavdevice/alsa-audio-common.c b/libavdevice/alsa-audio-common.c
new file mode 100644
index 0000000000..1cb2640998
--- /dev/null
+++ b/libavdevice/alsa-audio-common.c
@@ -0,0 +1,186 @@
+/*
+ * ALSA input and output
+ * Copyright (c) 2007 Luca Abeni ( lucabe72 email it )
+ * Copyright (c) 2007 Benoit Fouet ( benoit fouet free fr )
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file alsa-audio-common.c
+ * ALSA input and output: common code
+ * @author Luca Abeni ( lucabe72 email it )
+ * @author Benoit Fouet ( benoit fouet free fr )
+ * @author Nicolas George ( nicolas george normalesup org )
+ */
+
+#include "libavformat/avformat.h"
+#include <alsa/asoundlib.h>
+
+#include "alsa-audio.h"
+
+static av_cold snd_pcm_format_t codec_id_to_pcm_format(int codec_id)
+{
+    switch(codec_id) {
+        case CODEC_ID_PCM_S16LE: return SND_PCM_FORMAT_S16_LE;
+        case CODEC_ID_PCM_S16BE: return SND_PCM_FORMAT_S16_BE;
+        case CODEC_ID_PCM_S8:    return SND_PCM_FORMAT_S8;
+        default:                 return SND_PCM_FORMAT_UNKNOWN;
+    }
+}
+
+av_cold int ff_alsa_open(AVFormatContext *ctx, int mode,
+                         unsigned int *sample_rate,
+                         int channels, int *codec_id)
+{
+    AlsaData *s = ctx->priv_data;
+    const char *audio_device;
+    int res, flags = 0;
+    snd_pcm_format_t format;
+    snd_pcm_t *h;
+    snd_pcm_hw_params_t *hw_params;
+    snd_pcm_uframes_t buffer_size, period_size;
+
+    if (ctx->filename[0] == 0) audio_device = "default";
+    else                       audio_device = ctx->filename;
+
+    if (*codec_id == CODEC_ID_NONE)
+        *codec_id = DEFAULT_CODEC_ID;
+    format = codec_id_to_pcm_format(*codec_id);
+    if (format == SND_PCM_FORMAT_UNKNOWN) {
+        av_log(ctx, AV_LOG_ERROR, "sample format 0x%04x is not supported\n", *codec_id);
+        return AVERROR(ENOSYS);
+    }
+    s->frame_size = av_get_bits_per_sample(*codec_id) / 8 * channels;
+
+    if (ctx->flags & AVFMT_FLAG_NONBLOCK) {
+        flags = O_NONBLOCK;
+    }
+    res = snd_pcm_open(&h, audio_device, mode, flags);
+    if (res < 0) {
+        av_log(ctx, AV_LOG_ERROR, "cannot open audio device %s (%s)\n",
+               audio_device, snd_strerror(res));
+        return AVERROR_IO;
+    }
+
+    res = snd_pcm_hw_params_malloc(&hw_params);
+    if (res < 0) {
+        av_log(ctx, AV_LOG_ERROR, "cannot allocate hardware parameter structure (%s)\n",
+               snd_strerror(res));
+        goto fail1;
+    }
+
+    res = snd_pcm_hw_params_any(h, hw_params);
+    if (res < 0) {
+        av_log(ctx, AV_LOG_ERROR, "cannot initialize hardware parameter structure (%s)\n",
+               snd_strerror(res));
+        goto fail;
+    }
+
+    res = snd_pcm_hw_params_set_access(h, hw_params, SND_PCM_ACCESS_RW_INTERLEAVED);
+    if (res < 0) {
+        av_log(ctx, AV_LOG_ERROR, "cannot set access type (%s)\n",
+               snd_strerror(res));
+        goto fail;
+    }
+
+    res = snd_pcm_hw_params_set_format(h, hw_params, format);
+    if (res < 0) {
+        av_log(ctx, AV_LOG_ERROR, "cannot set sample format 0x%04x %d (%s)\n",
+               *codec_id, format, snd_strerror(res));
+        goto fail;
+    }
+
+    res = snd_pcm_hw_params_set_rate_near(h, hw_params, sample_rate, 0);
+    if (res < 0) {
+        av_log(ctx, AV_LOG_ERROR, "cannot set sample rate (%s)\n",
+               snd_strerror(res));
+        goto fail;
+    }
+
+    res = snd_pcm_hw_params_set_channels(h, hw_params, channels);
+    if (res < 0) {
+        av_log(ctx, AV_LOG_ERROR, "cannot set channel count to %d (%s)\n",
+               channels, snd_strerror(res));
+        goto fail;
+    }
+
+    snd_pcm_hw_params_get_buffer_size_max(hw_params, &buffer_size);
+    /* TODO: maybe use ctx->max_picture_buffer somehow */
+    res = snd_pcm_hw_params_set_buffer_size_near(h, hw_params, &buffer_size);
+    if (res < 0) {
+        av_log(ctx, AV_LOG_ERROR, "cannot set ALSA buffer size (%s)\n",
+               snd_strerror(res));
+        goto fail;
+    }
+
+    snd_pcm_hw_params_get_period_size_min(hw_params, &period_size, NULL);
+    res = snd_pcm_hw_params_set_period_size_near(h, hw_params, &period_size, NULL);
+    if (res < 0) {
+        av_log(ctx, AV_LOG_ERROR, "cannot set ALSA period size (%s)\n",
+               snd_strerror(res));
+        goto fail;
+    }
+    s->period_size = period_size;
+
+    res = snd_pcm_hw_params(h, hw_params);
+    if (res < 0) {
+        av_log(ctx, AV_LOG_ERROR, "cannot set parameters (%s)\n",
+               snd_strerror(res));
+        goto fail;
+    }
+
+    snd_pcm_hw_params_free(hw_params);
+
+    s->h = h;
+    return 0;
+
+fail:
+    snd_pcm_hw_params_free(hw_params);
+fail1:
+    snd_pcm_close(h);
+    return AVERROR_IO;
+}
+
+av_cold int ff_alsa_close(AVFormatContext *s1)
+{
+    AlsaData *s = s1->priv_data;
+
+    snd_pcm_close(s->h);
+    return 0;
+}
+
+int ff_alsa_xrun_recover(AVFormatContext *s1, int err)
+{
+    AlsaData *s = s1->priv_data;
+    snd_pcm_t *handle = s->h;
+
+    av_log(s1, AV_LOG_WARNING, "ALSA buffer xrun.\n");
+    if (err == -EPIPE) {
+        err = snd_pcm_prepare(handle);
+        if (err < 0) {
+            av_log(s1, AV_LOG_ERROR, "cannot recover from underrun (snd_pcm_prepare failed: %s)\n", snd_strerror(err));
+
+            return AVERROR_IO;
+        }
+    } else if (err == -ESTRPIPE) {
+        av_log(s1, AV_LOG_ERROR, "-ESTRPIPE... Unsupported!\n");
+
+        return -1;
+    }
+    return err;
+}