libswresample/swresample: avoid s16p internal transfer format

Instead use float one by default for sample rate conversions.
The s16p internal transfer format produces visible and hearable
quantization artifacts.

Signed-off-by: Paul B Mahol <onemda@gmail.com>

for S8 we continue to use S16 as it should have enough precision
Fate is adjusted so bitexactness is maintained between mips/arm/x86
if more tests became bit-inexact on some platform, the same change
can be done to them

The use of higher precision and float intermediates inevitably
leads to more differences between platforms.

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libswresample/swresample.c

@@ -331,8 +331,14 @@ av_cold int swr_init(struct SwrContext *s){
                  s->rematrix_custom;
 
     if(s->int_sample_fmt == AV_SAMPLE_FMT_NONE){
+        // 16bit or less to 16bit or less with the same sample rate
         if(   av_get_bytes_per_sample(s-> in_sample_fmt) <= 2
-           && av_get_bytes_per_sample(s->out_sample_fmt) <= 2){
+           && av_get_bytes_per_sample(s->out_sample_fmt) <= 2
+           && s->out_sample_rate==s->in_sample_rate) {
+            s->int_sample_fmt= AV_SAMPLE_FMT_S16P;
+        // 8 -> 8, 16->8, 8->16bit
+        } else if(   av_get_bytes_per_sample(s-> in_sample_fmt)
+                    +av_get_bytes_per_sample(s->out_sample_fmt) <= 3 ) {
             s->int_sample_fmt= AV_SAMPLE_FMT_S16P;
         }else if(   av_get_bytes_per_sample(s-> in_sample_fmt) <= 2
            && !s->rematrix

tests/fate/acodec.mak

@@ -156,14 +156,14 @@ fate-acodec-ra144: CMP_SHIFT = -320
 FATE_ACODEC-$(call ENCDEC, ROQ_DPCM, ROQ, ARESAMPLE_FILTER) += fate-acodec-roqaudio
 fate-acodec-roqaudio: FMT = roq
 fate-acodec-roqaudio: CODEC = roq_dpcm
-fate-acodec-roqaudio: ENCOPTS = -ar 22050
-fate-acodec-roqaudio: DECOPTS = -ar 44100
+fate-acodec-roqaudio: ENCOPTS = -af aresample=22050:tsf=s16p
+fate-acodec-roqaudio: DECOPTS = -af aresample=44100:tsf=s16p
 
 FATE_ACODEC-$(call ENCDEC, S302M, MPEGTS, ARESAMPLE_FILTER) += fate-acodec-s302m
 fate-acodec-s302m: FMT = mpegts
 fate-acodec-s302m: CODEC = s302m
-fate-acodec-s302m: ENCOPTS = -ar 48000 -strict -2
-fate-acodec-s302m: DECOPTS = -ar 44100
+fate-acodec-s302m: ENCOPTS = -af aresample=48000:tsf=s16p -strict -2
+fate-acodec-s302m: DECOPTS = -af aresample=44100:tsf=s16p
 
 FATE_ACODEC-$(call ENCDEC, WAVPACK, WV, ARESAMPLE_FILTER) += fate-acodec-wavpack
 fate-acodec-wavpack: FMT = wv

tests/fate/lavf-container.mak

@@ -39,13 +39,13 @@ $(FATE_LAVF_CONTAINER): $(AREF) $(VREF)
 fate-lavf-asf: CMD = lavf_container "" "-c:a mp2 -ar 44100" "-r 25"
 fate-lavf-avi fate-lavf-nut: CMD = lavf_container "" "-c:a mp2 -ar 44100 -threads 1"
 fate-lavf-dv:  CMD = lavf_container "-ar 48000 -channel_layout stereo" "-r 25 -s pal"
-fate-lavf-dv_pal:  CMD = lavf_container_timecode_nodrop "-ar 48000 -r 25 -s pal -ac 2 -f dv"
-fate-lavf-dv_ntsc:  CMD = lavf_container_timecode_drop "-ar 48000 -pix_fmt yuv411p -s ntsc -ac 2 -f dv"
+fate-lavf-dv_pal:  CMD = lavf_container_timecode_nodrop "-af aresample=48000:tsf=s16p -r 25 -s pal -ac 2 -f dv"
+fate-lavf-dv_ntsc:  CMD = lavf_container_timecode_drop "-af aresample=48000:tsf=s16p -pix_fmt yuv411p -s ntsc -ac 2 -f dv"
 fate-lavf-flv fate-lavf-swf: CMD = lavf_container "" "-an"
 fate-lavf-flm: CMD = lavf_container "" "-pix_fmt rgba"
 fate-lavf-gxf: CMD = lavf_container "-ar 48000" "-r 25 -s pal -ac 1 -threads 1"
-fate-lavf-gxf_pal: CMD = lavf_container_timecode_nodrop "-ar 48000 -r 25 -s pal -ac 1 -threads 1 -f gxf"
-fate-lavf-gxf_ntsc: CMD = lavf_container_timecode_drop "-ar 48000 -s ntsc -ac 1 -threads 1 -f gxf"
+fate-lavf-gxf_pal: CMD = lavf_container_timecode_nodrop "-af aresample=48000:tsf=s16p -r 25 -s pal -ac 1 -threads 1 -f gxf"
+fate-lavf-gxf_ntsc: CMD = lavf_container_timecode_drop "-af aresample=48000:tsf=s16p -s ntsc -ac 1 -threads 1 -f gxf"
 fate-lavf-ismv: CMD = lavf_container_timecode "-an -write_tmcd 1 -c:v mpeg4 -threads 1"
 fate-lavf-mkv: CMD = lavf_container "" "-c:a mp2 -c:v mpeg4 -ar 44100 -threads 1"
 fate-lavf-mkv_attachment: CMD = lavf_container_attach "-c:a mp2 -c:v mpeg4 -threads 1 -f matroska"
@@ -53,7 +53,7 @@ fate-lavf-mov: CMD = lavf_container_timecode "-movflags +faststart -c:a pcm_alaw
 fate-lavf-mov_rtphint: CMD = lavf_container "" "-movflags +rtphint -c:a pcm_alaw -c:v mpeg4 -threads 1 -f mov"
 fate-lavf-mp4: CMD = lavf_container_timecode "-c:v mpeg4 -an -threads 1"
 fate-lavf-mpg: CMD = lavf_container_timecode "-ar 44100 -threads 1"
-fate-lavf-mxf: CMD = lavf_container_timecode "-ar 48000 -bf 2 -threads 1"
+fate-lavf-mxf: CMD = lavf_container_timecode "-af aresample=48000:tsf=s16p -bf 2 -threads 1"
 fate-lavf-mxf_d10: CMD = lavf_container "-ar 48000 -ac 2" "-r 25 -vf scale=720:576,pad=720:608:0:32,setfield=tff -c:v mpeg2video -g 0 -flags +ildct+low_delay -dc 10 -non_linear_quant 1 -intra_vlc 1 -qscale 1 -ps 1 -qmin 1 -rc_max_vbv_use 1 -rc_min_vbv_use 1 -pix_fmt yuv422p -minrate 30000k -maxrate 30000k -b 30000k -bufsize 1200000 -rc_init_occupancy 1200000 -qmax 12 -f mxf_d10"
 fate-lavf-mxf_dv25: CMD = lavf_container "-ar 48000 -ac 2" "-r 25 -vf scale=720:576,setdar=4/3,setfield=bff -c:v dvvideo -pix_fmt yuv420p -b 25000k -f mxf"
 fate-lavf-mxf_dvcpro50: CMD = lavf_container "-ar 48000 -ac 2" "-r 25 -vf scale=720:576,setdar=16/9,setfield=bff -c:v dvvideo -pix_fmt yuv422p -b 50000k -f mxf"