[FFmpeg-devel] [PATCH] avdevice/alsa_dec: add a ch_layout option

* [FFmpeg-devel] [PATCH] avdevice/alsa_dec: add a ch_layout option
@ 2025-01-28 12:57 James Almer
  2025-02-01  1:43 ` Michael Niedermayer
  0 siblings, 1 reply; 5+ messages in thread
From: James Almer @ 2025-01-28 12:57 UTC (permalink / raw)
  To: ffmpeg-devel

Missed in ffc4fd3cc2ccb2cadb71f19849842b18ca1281c6, which after
e78173557da898f18a78241cc3525b76694164b5 broke setting channel count.

Should fix ticket #11434.

Signed-off-by: James Almer <jamrial@gmail.com>
---
 libavdevice/alsa.h          |  4 ++++
 libavdevice/alsa_dec.c      | 24 +++++++++++++++++++-----
 libavdevice/version_major.h |  1 +
 3 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/libavdevice/alsa.h b/libavdevice/alsa.h
index 07783c983a..3e1ba31384 100644
--- a/libavdevice/alsa.h
+++ b/libavdevice/alsa.h
@@ -35,6 +35,7 @@
 #include "libavutil/log.h"
 #include "timefilter.h"
 #include "avdevice.h"
+#include "version.h"
 
 /* XXX: we make the assumption that the soundcard accepts this format */
 /* XXX: find better solution with "preinit" method, needed also in
@@ -51,7 +52,10 @@ typedef struct AlsaData {
     int frame_size;  ///< bytes per sample * channels
     int period_size; ///< preferred size for reads and writes, in frames
     int sample_rate; ///< sample rate set by user
+#if FF_API_ALSA_CHANNELS
     int channels;    ///< number of channels set by user
+#endif
+    AVChannelLayout ch_layout; ///< Channel layout set by user
     int last_period;
     TimeFilter *timefilter;
     void (*reorder_func)(const void *, void *, int);
diff --git a/libavdevice/alsa_dec.c b/libavdevice/alsa_dec.c
index 018afaef08..b037c0bf1b 100644
--- a/libavdevice/alsa_dec.c
+++ b/libavdevice/alsa_dec.c
@@ -73,7 +73,14 @@ static av_cold int audio_read_header(AVFormatContext *s1)
     }
     codec_id    = s1->audio_codec_id;
 
-    ret = ff_alsa_open(s1, SND_PCM_STREAM_CAPTURE, &s->sample_rate, s->channels,
+#if FF_API_ALSA_CHANNELS
+    if (s->channels > 0) {
+        av_channel_layout_uninit(&s->ch_layout);
+        s->ch_layout.nb_channels = s->channels;
+    }
+#endif
+
+    ret = ff_alsa_open(s1, SND_PCM_STREAM_CAPTURE, &s->sample_rate, s->ch_layout.nb_channels,
         &codec_id);
     if (ret < 0) {
         return AVERROR(EIO);
@@ -83,20 +90,24 @@ static av_cold int audio_read_header(AVFormatContext *s1)
     st->codecpar->codec_type  = AVMEDIA_TYPE_AUDIO;
     st->codecpar->codec_id    = codec_id;
     st->codecpar->sample_rate = s->sample_rate;
-    st->codecpar->ch_layout.nb_channels = s->channels;
+    ret = av_channel_layout_copy(&st->codecpar->ch_layout, &s->ch_layout);
+    if (ret < 0)
+        goto fail;
     st->codecpar->frame_size = s->frame_size;
     avpriv_set_pts_info(st, 64, 1, 1000000);  /* 64 bits pts in us */
     /* microseconds instead of seconds, MHz instead of Hz */
     s->timefilter = ff_timefilter_new(1000000.0 / s->sample_rate,
                                       s->period_size, 1.5E-6);
-    if (!s->timefilter)
+    if (!s->timefilter) {
+        ret = AVERROR(EIO);
         goto fail;
+    }
 
     return 0;
 
 fail:
     snd_pcm_close(s->h);
-    return AVERROR(EIO);
+    return ret;
 }
 
 static int audio_read_packet(AVFormatContext *s1, AVPacket *pkt)
@@ -146,7 +157,10 @@ static int audio_get_device_list(AVFormatContext *h, AVDeviceInfoList *device_li
 
 static const AVOption options[] = {
     { "sample_rate", "", offsetof(AlsaData, sample_rate), AV_OPT_TYPE_INT, {.i64 = 48000}, 1, INT_MAX, AV_OPT_FLAG_DECODING_PARAM },
-    { "channels",    "", offsetof(AlsaData, channels),    AV_OPT_TYPE_INT, {.i64 = 2},     1, INT_MAX, AV_OPT_FLAG_DECODING_PARAM },
+#if FF_API_ALSA_CHANNELS
+    { "channels",    "", offsetof(AlsaData, channels),    AV_OPT_TYPE_INT, {.i64 = 0},     0, INT_MAX, AV_OPT_FLAG_DECODING_PARAM | AV_OPT_FLAG_DEPRECATED },
+#endif
+    { "ch_layout",   "", offsetof(AlsaData, ch_layout),   AV_OPT_TYPE_CH_LAYOUT, {.str = "2C"}, INT_MIN, INT_MAX, AV_OPT_FLAG_DECODING_PARAM },
     { NULL },
 };
 
diff --git a/libavdevice/version_major.h b/libavdevice/version_major.h
index f16abb6909..50f577f295 100644
--- a/libavdevice/version_major.h
+++ b/libavdevice/version_major.h
@@ -39,5 +39,6 @@
 #define FF_API_OPENGL_DEVICE (LIBAVDEVICE_VERSION_MAJOR < 62)
 // reminder to remove the sdl2 device on next major bump
 #define FF_API_SDL2_DEVICE (LIBAVDEVICE_VERSION_MAJOR < 62)
+#define FF_API_ALSA_CHANNELS (LIBAVDEVICE_VERSION_MAJOR < 62)
 
 #endif /* AVDEVICE_VERSION_MAJOR_H */
-- 
2.48.1

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