Fix 5.1/7.1 .at3 LFE channel order [Devil May Cry 4 (PS3)]

src/coding/coding.h

@@ -291,6 +291,7 @@ void free_ffmpeg(ffmpeg_codec_data *data);
 
 void ffmpeg_set_skip_samples(ffmpeg_codec_data * data, int skip_samples);
 uint32_t ffmpeg_get_channel_layout(ffmpeg_codec_data * data);
+void ffmpeg_set_channel_remapping(ffmpeg_codec_data * data, int *channels_remap);
 
 /* ffmpeg_decoder_custom_opus.c (helper-things) */
 ffmpeg_codec_data * init_ffmpeg_switch_opus(STREAMFILE *streamFile, off_t start_offset, size_t data_size, int channels, int skip, int sample_rate);

src/coding/ffmpeg_decoder.c

@@ -28,6 +28,25 @@ static void g_init_ffmpeg() {
     }
 }
 
+static void remap_audio(sample_t *outbuf, int sample_count, int channels, int channel_mappings[]) {
+    int ch_from,ch_to,s;
+    sample_t temp;
+    for (s = 0; s < sample_count; s++) {
+        for (ch_from = 0; ch_from < channels; ch_from++) {
+            if (ch_from > 32)
+                continue;
+
+            ch_to = channel_mappings[ch_from];
+            if (ch_to < 1 || ch_to > 32 || ch_to > channels-1 || ch_from == ch_to)
+                continue;
+
+            temp = outbuf[s*channels + ch_from];
+            outbuf[s*channels + ch_from] = outbuf[s*channels + ch_to];
+            outbuf[s*channels + ch_to] = temp;
+        }
+    }
+}
+
 /* converts codec's samples (can be in any format, ex. Ogg's float32) to PCM16 */
 static void convert_audio_pcm16(sample_t *outbuf, const uint8_t *inbuf, int fullSampleCount, int bitsPerSample, int floatingPoint) {
     int s;
@@ -656,6 +675,8 @@ end:
     /* convert native sample format into PCM16 outbuf */
     samplesReadNow = bytesRead / (bytesPerSample * channels);
     convert_audio_pcm16(outbuf, data->sampleBuffer, samplesReadNow * channels, data->bitsPerSample, data->floatingPoint);
+    if (data->channel_remap_set)
+        remap_audio(outbuf, samplesReadNow, data->channels, data->channel_remap);
 
     /* clean buffer when requested more samples than possible */
     if (endOfAudio && samplesReadNow < samples_to_do) {
@@ -814,4 +835,19 @@ uint32_t ffmpeg_get_channel_layout(ffmpeg_codec_data * data) {
     return (uint32_t)data->codecCtx->channel_layout; /* uint64 but there ain't so many speaker mappings */
 }
 
+/* yet another hack to fix codecs that encode channels in different order and reorder on decoder
+ * but FFmpeg doesn't do it automatically
+ * (maybe should be done via mixing, but could clash with other stuff?) */
+void ffmpeg_set_channel_remapping(ffmpeg_codec_data * data, int *channel_remap) {
+    int i;
+
+    if (data->channels > 32)
+        return;
+
+    for (i = 0; i < data->channels; i++) {
+        data->channel_remap[i] = channel_remap[i];
+    }
+    data->channel_remap_set = 1;
+}
+
 #endif

src/meta/riff.c

@@ -608,6 +608,21 @@ VGMSTREAM * init_vgmstream_riff(STREAMFILE *streamFile) {
                     ffmpeg_set_skip_samples(ffmpeg_data, fact_sample_skip);
                 }
 
+                /* LFE channel should be reordered on decode, but FFmpeg doesn't do it automatically:
+                 * - 6ch: FL FR FC BL BR LFE > FL FR FC LFE BL BR
+                 * - 8ch: FL FR FC BL BR SL SR LFE > FL FR FC LFE BL BR SL SR
+                 * (ATRAC3Plus only, 5/7ch can't be encoded) */
+                if (ffmpeg_data->channels == 6) {
+                    /* LFE BR BL > LFE BL BR > same */
+                    int channel_remap[] = { 0, 1, 2, 5, 5, 5, };
+                    ffmpeg_set_channel_remapping(ffmpeg_data, channel_remap);
+                }
+                else if (ffmpeg_data->channels == 8) {
+                    /* LFE BR SL SR BL > LFE BL SL SR BR > LFE BL BR SR SL > LFE BL BR SL SR > same */
+                    int channel_remap[] = { 0, 1, 2, 7, 7, 7, 7, 7};
+                    ffmpeg_set_channel_remapping(ffmpeg_data, channel_remap);
+                }
+
                 /* RIFF loop/sample values are absolute (with skip samples), adjust */
                 if (loop_flag) {
                     loop_start_smpl -= (int32_t)ffmpeg_data->skipSamples;

src/vgmstream.h

@@ -1205,6 +1205,9 @@ typedef struct {
     int64_t skipSamples; // number of start samples that will be skipped (encoder delay), for looping adjustments
     int streamCount; // number of FFmpeg audio streams
     
+    int channel_remap_set;
+    int channel_remap[32]; /* map of channel > new position */
+
     /*** internal state ***/
     // Intermediate byte buffer
     uint8_t *sampleBuffer;