[FFmpeg-devel] [PATCH] ffprobe/eac3/mlp/dca: add detection of spatial audio extensions

[Marth64 <marth64@proxyid.net>]

Signed-off-by: Marth64 <marth64@proxyid.net>
---
Adds detection of spatial/object-based audio extensions in E-AC-3,
TrueHD, and DCA XLL (DTS). This includes Atmos, DTS:X, and IMAX formats.
Please let me know what I could improve, I'm learning still.
Thank you.

 doc/ffprobe.xsd            |  1 +
 fftools/ffprobe.c          |  3 +++
 libavcodec/ac3dec.c        |  1 +
 libavcodec/ac3dec.h        |  1 +
 libavcodec/avcodec.h       |  6 ++++++
 libavcodec/codec_par.c     |  2 ++
 libavcodec/codec_par.h     |  6 ++++++
 libavcodec/dca_syncwords.h |  3 +++
 libavcodec/dca_xll.c       | 14 ++++++++++++++
 libavcodec/eac3dec.c       | 11 ++++++++++-
 libavcodec/mlpdec.c        |  9 +++++++++
 11 files changed, 56 insertions(+), 1 deletion(-)

diff --git a/doc/ffprobe.xsd b/doc/ffprobe.xsd
index 0920380108..a01a4359dc 100644
--- a/doc/ffprobe.xsd
+++ b/doc/ffprobe.xsd
@@ -247,6 +247,7 @@
       <xsd:attribute name="channel_layout"   type="xsd:string"/>
       <xsd:attribute name="bits_per_sample"  type="xsd:int"/>
       <xsd:attribute name="initial_padding"  type="xsd:int"/>
+      <xsd:attribute name="spatial_ext"      type="xsd:boolean"/>
 
       <xsd:attribute name="id"               type="xsd:string"/>
       <xsd:attribute name="r_frame_rate"     type="xsd:string" use="required"/>
diff --git a/fftools/ffprobe.c b/fftools/ffprobe.c
index dfa7ff1b24..7e81088c56 100644
--- a/fftools/ffprobe.c
+++ b/fftools/ffprobe.c
@@ -3071,6 +3071,9 @@ static int show_stream(WriterContext *w, AVFormatContext *fmt_ctx, int stream_id
         print_int("bits_per_sample", av_get_bits_per_sample(par->codec_id));
 
         print_int("initial_padding", par->initial_padding);
+        if (par->spatial_ext > 0) {
+            print_int("spatial_ext",  par->spatial_ext);
+        }
         break;
 
     case AVMEDIA_TYPE_SUBTITLE:
diff --git a/libavcodec/ac3dec.c b/libavcodec/ac3dec.c
index 0b120e6140..009acd9ff6 100644
--- a/libavcodec/ac3dec.c
+++ b/libavcodec/ac3dec.c
@@ -1714,6 +1714,7 @@ skip:
     if (!err) {
         avctx->sample_rate = s->sample_rate;
         avctx->bit_rate    = s->bit_rate + s->prev_bit_rate;
+        avctx->spatial_ext = s->eac3_extension_type_a == 1;
     }
 
     if (!avctx->sample_rate) {
diff --git a/libavcodec/ac3dec.h b/libavcodec/ac3dec.h
index 138b462abb..0829f4b40d 100644
--- a/libavcodec/ac3dec.h
+++ b/libavcodec/ac3dec.h
@@ -102,6 +102,7 @@ typedef struct AC3DecodeContext {
     int eac3;                               ///< indicates if current frame is E-AC-3
     int eac3_frame_dependent_found;         ///< bitstream has E-AC-3 dependent frame(s)
     int eac3_subsbtreamid_found;            ///< bitstream has E-AC-3 additional substream(s)
+    int eac3_extension_type_a;              ///< bitstream has E-AC-3 extension type A enabled frame(s)
     int dolby_surround_mode;                ///< dolby surround mode                    (dsurmod)
     int dolby_surround_ex_mode;             ///< dolby surround ex mode                 (dsurexmod)
     int dolby_headphone_mode;               ///< dolby headphone mode                   (dheadphonmod)
diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
index 755e543fac..8b54a99313 100644
--- a/libavcodec/avcodec.h
+++ b/libavcodec/avcodec.h
@@ -2104,6 +2104,12 @@ typedef struct AVCodecContext {
      *             The decoder can then override during decoding as needed.
      */
     AVChannelLayout ch_layout;
+
+    /**
+     * Audio only. Whether or not a spatial audio extension is
+     * detected in the stream (object-based surround).
+     */
+    int spatial_ext;
 } AVCodecContext;
 
 /**
diff --git a/libavcodec/codec_par.c b/libavcodec/codec_par.c
index abda649aa8..02f6da5059 100644
--- a/libavcodec/codec_par.c
+++ b/libavcodec/codec_par.c
@@ -161,6 +161,7 @@ FF_ENABLE_DEPRECATION_WARNINGS
         par->initial_padding  = codec->initial_padding;
         par->trailing_padding = codec->trailing_padding;
         par->seek_preroll     = codec->seek_preroll;
+        par->spatial_ext      = codec->spatial_ext;
         break;
     case AVMEDIA_TYPE_SUBTITLE:
         par->width  = codec->width;
@@ -243,6 +244,7 @@ FF_ENABLE_DEPRECATION_WARNINGS
         codec->initial_padding  = par->initial_padding;
         codec->trailing_padding = par->trailing_padding;
         codec->seek_preroll     = par->seek_preroll;
+        codec->spatial_ext      = par->spatial_ext;
         break;
     case AVMEDIA_TYPE_SUBTITLE:
         codec->width  = par->width;
diff --git a/libavcodec/codec_par.h b/libavcodec/codec_par.h
index f51d27c590..287b138b6b 100644
--- a/libavcodec/codec_par.h
+++ b/libavcodec/codec_par.h
@@ -211,6 +211,12 @@ typedef struct AVCodecParameters {
      * Audio only. The channel layout and number of channels.
      */
     AVChannelLayout ch_layout;
+
+    /**
+     * Audio only. Whether or not a spatial audio extension is
+     * detected in the stream (object-based surround).
+     */
+    int spatial_ext;
 } AVCodecParameters;
 
 /**
diff --git a/libavcodec/dca_syncwords.h b/libavcodec/dca_syncwords.h
index 4d2cd5f56d..ccbc38bb38 100644
--- a/libavcodec/dca_syncwords.h
+++ b/libavcodec/dca_syncwords.h
@@ -33,4 +33,7 @@
 #define    DCA_SYNCWORD_SUBSTREAM_CORE       0x02B09261U
 #define    DCA_SYNCWORD_REV1AUX              0x9A1105A0U
 
+#define    DCA_SYNCWORD_XLL_X                0x20008
+#define    DCA_SYNCWORD_XLL_IMAX             (0xF14000D0 >> 1)
+
 #endif /* AVCODEC_DCA_SYNCWORDS_H */
diff --git a/libavcodec/dca_xll.c b/libavcodec/dca_xll.c
index fe2c766d98..6b64f907cc 100644
--- a/libavcodec/dca_xll.c
+++ b/libavcodec/dca_xll.c
@@ -1043,6 +1043,7 @@ static int parse_band_data(DCAXllDecoder *s)
 static int parse_frame(DCAXllDecoder *s, const uint8_t *data, int size, DCAExssAsset *asset)
 {
     int ret;
+    int extradata_peek_pos;
 
     if ((ret = init_get_bits8(&s->gb, data, size)) < 0)
         return ret;
@@ -1054,10 +1055,23 @@ static int parse_frame(DCAXllDecoder *s, const uint8_t *data, int size, DCAExssA
         return ret;
     if ((ret = parse_band_data(s)) < 0)
         return ret;
+
+    extradata_peek_pos = (get_bits_count(&s->gb) + 31) & ~31;
+    if (s->frame_size * 8 > extradata_peek_pos) {
+        unsigned int extradata_syncword = show_bits(&s->gb, 32);
+
+        if (extradata_syncword == DCA_SYNCWORD_XLL_X) {
+            s->avctx->spatial_ext = 1;
+        } else if ((extradata_syncword >> 1) == DCA_SYNCWORD_XLL_IMAX) {
+            s->avctx->spatial_ext = 1;
+        }
+    }
+
     if (ff_dca_seek_bits(&s->gb, s->frame_size * 8)) {
         av_log(s->avctx, AV_LOG_ERROR, "Read past end of XLL frame\n");
         return AVERROR_INVALIDDATA;
     }
+
     return ret;
 }
 
diff --git a/libavcodec/eac3dec.c b/libavcodec/eac3dec.c
index deca51dd3d..5c71751a0c 100644
--- a/libavcodec/eac3dec.c
+++ b/libavcodec/eac3dec.c
@@ -464,7 +464,16 @@ static int ff_eac3_parse_header(AC3DecodeContext *s)
     if (get_bits1(gbc)) {
         int addbsil = get_bits(gbc, 6);
         for (i = 0; i < addbsil + 1; i++) {
-            skip_bits(gbc, 8); // skip additional bit stream info
+            if (i == 0) {
+                /* In this 8 bit chunk, the LSB is equal to flag_ec3_extension_type_a
+                   which can be used to detect Atmos presence */
+                skip_bits(gbc, 7);
+                if (get_bits1(gbc)) {
+                    s->eac3_extension_type_a = 1;
+                }
+            } else {
+                skip_bits(gbc, 8); // skip additional bit stream info
+            }
         }
     }
 
diff --git a/libavcodec/mlpdec.c b/libavcodec/mlpdec.c
index 0ee1f0982c..547e68342e 100644
--- a/libavcodec/mlpdec.c
+++ b/libavcodec/mlpdec.c
@@ -392,6 +392,15 @@ static int read_major_sync(MLPDecodeContext *m, GetBitContext *gb)
     m->num_substreams        = mh.num_substreams;
     m->substream_info        = mh.substream_info;
 
+    /*  If there is a 4th substream and the MSB of substream_info is set,
+     *  there is a 16-channel spatial presentation (Atmos in TrueHD).
+     */
+    if (m->avctx->codec_id == AV_CODEC_ID_TRUEHD
+            && m->num_substreams == 4
+            && m->substream_info >> 7 == 1) {
+        m->avctx->spatial_ext = 1;
+    }
+
     /* limit to decoding 3 substreams, as the 4th is used by Dolby Atmos for non-audio data */
     m->max_decoded_substream = FFMIN(m->num_substreams - 1, 2);
 
-- 
2.25.1

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