Revert "libopus: Add channel mapping 2 support in libopusdec"

This reverts commit c8c995bc.

libavcodec/libopusdec.c

@@ -63,6 +63,8 @@ static av_cold int libopus_decode_init(AVCodecContext *avc)
     avc->sample_rate    = 48000;
     avc->sample_fmt     = avc->request_sample_fmt == AV_SAMPLE_FMT_FLT ?
                           AV_SAMPLE_FMT_FLT : AV_SAMPLE_FMT_S16;
+    avc->channel_layout = avc->channels > 8 ? 0 :
+                          ff_vorbis_channel_layouts[avc->channels - 1];
 
     if (avc->extradata_size >= OPUS_HEAD_SIZE) {
         opus->pre_skip = AV_RL16(avc->extradata + 10);
@@ -86,35 +88,14 @@ static av_cold int libopus_decode_init(AVCodecContext *avc)
         mapping    = mapping_arr;
     }
 
-    if (channel_map == 1) {
-        avc->channel_layout = avc->channels > 8 ? 0 :
-                              ff_vorbis_channel_layouts[avc->channels - 1];
-        if (avc->channels > 2 && avc->channels <= 8) {
-            const uint8_t *vorbis_offset = ff_vorbis_channel_layout_offsets[avc->channels - 1];
-            int ch;
-
-            /* Remap channels from Vorbis order to ffmpeg order */
-            for (ch = 0; ch < avc->channels; ch++)
-                mapping_arr[ch] = mapping[vorbis_offset[ch]];
-            mapping = mapping_arr;
-        }
-    } else if (channel_map == 2) {
-        int ambisonic_order = ff_sqrt(avc->channels) - 1;
-        if (avc->channels != (ambisonic_order + 1) * (ambisonic_order + 1) &&
-            avc->channels != (ambisonic_order + 1) * (ambisonic_order + 1) + 2) {
-            av_log(avc, AV_LOG_ERROR,
-                   "Channel mapping 2 is only specified for channel counts"
-                   " which can be written as (n + 1)^2 or (n + 2)^2 + 2"
-                   " for nonnegative integer n\n");
-            return AVERROR_INVALIDDATA;
-        }
-        if (avc->channels > 227) {
-            av_log(avc, AV_LOG_ERROR, "Too many channels\n");
-            return AVERROR_INVALIDDATA;
-        }
-        avc->channel_layout = 0;
-    } else {
-        avc->channel_layout = 0;
+    if (avc->channels > 2 && avc->channels <= 8) {
+        const uint8_t *vorbis_offset = ff_vorbis_channel_layout_offsets[avc->channels - 1];
+        int ch;
+
+        /* Remap channels from Vorbis order to ffmpeg order */
+        for (ch = 0; ch < avc->channels; ch++)
+            mapping_arr[ch] = mapping[vorbis_offset[ch]];
+        mapping = mapping_arr;
     }
 
     opus->dec = opus_multistream_decoder_create(avc->sample_rate, avc->channels,