[FFmpeg-devel] [PATCH] avcodec/audiotoolboxdec: Decode appropriate formats to float

[Christopher Snowhill]

These candidate formats are likely already decoded in floating point
internally anyway, so request float output so that it's also possible
to clip or peak level as necessary.

Signed-off-by: Christopher Snowhill <kode54 at gmail.com>
---
 libavcodec/audiotoolboxdec.c | 36 ++++++++++++++++++++++++++++++++----
 1 file changed, 32 insertions(+), 4 deletions(-)

diff --git a/libavcodec/audiotoolboxdec.c b/libavcodec/audiotoolboxdec.c
index 4abcb63a03..427f143468 100644
--- a/libavcodec/audiotoolboxdec.c
+++ b/libavcodec/audiotoolboxdec.c
@@ -297,6 +297,25 @@ static int ffat_set_extradata(AVCodecContext *avctx)
     return 0;
 }
 
+static bool ffat_get_format_is_float(enum AVCodecID codec)
+{
+    switch (codec) {
+    case AV_CODEC_ID_AAC:
+    case AV_CODEC_ID_AC3:
+    case AV_CODEC_ID_AMR_NB:
+    case AV_CODEC_ID_EAC3:
+    case AV_CODEC_ID_ILBC:
+    case AV_CODEC_ID_MP1:
+    case AV_CODEC_ID_MP2:
+    case AV_CODEC_ID_MP3:
+    case AV_CODEC_ID_QDMC:
+    case AV_CODEC_ID_QDM2:
+        return true;
+    default:
+        return false;
+    }
+}
+
 static av_cold int ffat_create_decoder(AVCodecContext *avctx,
                                        const AVPacket *pkt)
 {
@@ -304,8 +323,12 @@ static av_cold int ffat_create_decoder(AVCodecContext *avctx,
     OSStatus status;
     int i;
 
-    enum AVSampleFormat sample_fmt = (avctx->bits_per_raw_sample == 32) ?
-                                     AV_SAMPLE_FMT_S32 : AV_SAMPLE_FMT_S16;
+    bool sample_fmt_is_float = ffat_get_format_is_float(avctx->codec_id);
+
+    enum AVSampleFormat sample_fmt = sample_fmt_is_float ?
+                                     AV_SAMPLE_FMT_FLT :
+                                     ((avctx->bits_per_raw_sample == 32) ?
+                                     AV_SAMPLE_FMT_S32 : AV_SAMPLE_FMT_S16);
 
     AudioStreamBasicDescription in_format = {
         .mFormatID = ffat_get_format_id(avctx->codec_id, avctx->profile),
@@ -313,7 +336,10 @@ static av_cold int ffat_create_decoder(AVCodecContext *avctx,
     };
     AudioStreamBasicDescription out_format = {
         .mFormatID = kAudioFormatLinearPCM,
-        .mFormatFlags = kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsPacked,
+        .mFormatFlags = (sample_fmt_is_float ?
+                        kAudioFormatFlagIsFloat :
+                        kAudioFormatFlagIsSignedInteger) |
+                        kAudioFormatFlagIsPacked,
         .mFramesPerPacket = 1,
         .mBitsPerChannel = av_get_bytes_per_sample(sample_fmt) * 8,
     };
@@ -471,7 +497,9 @@ static OSStatus ffat_decode_callback(AudioConverterRef converter, UInt32 *nb_pac
 static void ffat_copy_samples(AVCodecContext *avctx, AVFrame *frame)
 {
     ATDecodeContext *at = avctx->priv_data;
-    if (avctx->sample_fmt == AV_SAMPLE_FMT_S32) {
+    if (avctx->sample_fmt == AV_SAMPLE_FMT_FLT) {
+        COPY_SAMPLES(float);
+    } else if (avctx->sample_fmt == AV_SAMPLE_FMT_S32) {
         COPY_SAMPLES(int32_t);
     } else {
         COPY_SAMPLES(int16_t);
-- 
2.32.0 (Apple Git-132)