This allows libavcodec/opus to demux ambisonics in an ogg/opus container.
Channel mapping family 2 is being added in this standards track IETF draft:
tools.ietf.org/html/draft-ietf-codec-ambisonics-00
---
libavcodec/opus.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
diff --git a/libavcodec/opus.c b/libavcodec/opus.c
index 703d2e8..db758e9 100644
--- a/libavcodec/opus.c
+++ b/libavcodec/opus.c
@@ -328,7 +328,7 @@ av_cold int ff_opus_parse_extradata(AVCodecContext *avctx,
channels = avctx->extradata ? extradata[9] : (avctx->channels == 1) ? 1 :
2;
if (!channels) {
- av_log(avctx, AV_LOG_ERROR, "Zero channel count specified in the
extadata\n");
+ av_log(avctx, AV_LOG_ERROR, "Zero channel count specified in the
extradata\n");
return AVERROR_INVALIDDATA;
}
@@ -347,7 +347,7 @@ av_cold int ff_opus_parse_extradata(AVCodecContext *avctx,
streams = 1;
stereo_streams = channels - 1;
channel_map = default_channel_map;
- } else if (map_type == 1 || map_type == 255) {
+ } else if (map_type == 1 || map_type == 2 || map_type == 255) {
if (extradata_size < 21 + channels) {
av_log(avctx, AV_LOG_ERROR, "Invalid extradata size: %d\n",
extradata_size);
@@ -371,6 +371,15 @@ av_cold int ff_opus_parse_extradata(AVCodecContext *avctx,
}
layout = ff_vorbis_channel_layouts[channels - 1];
channel_reorder = channel_reorder_vorbis;
+ } else if (map_type == 2) {
+ int ambisonic_order = ((int)sqrt(channels)) - 1;
+ if (channels != (ambisonic_order + 1) * (ambisonic_order + 1)) {
+ av_log(avctx, AV_LOG_ERROR,
+ "Channel mapping 2 is only specified for channel counts"
+ " which can be written as (n + 1)^2 for nonnegative
integer n\n");
+ return AVERROR_INVALIDDATA;
+ }
+ layout = 0;
} else
layout = 0;
--
2.8.0.rc3.226.g39d4020
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