avcodec/wmadec: fix WMA gapless playback

Fixes trac issue #7473.

Removes encoder delay (skip samples) and writes remaining frame samples after EOF to get correct sample count.

Output is now accurate vs players that use Microsoft's codecs (Windows Media Format Runtime).

Tested vs encode>decode WMAv2 with MS's codecs and most sample rate/bit rate/channel/mode combinations in ASF/XWMA.
WMAv1 appears to use the same delay, from FFmpeg samples.

Signed-off-by: bnnm <bananaman255@gmail.com>

4 files changed, 27 insertions, 8 deletions

diff --git a/libavcodec/wma.h b/libavcodec/wma.h
index aea7ba28ab..80e52687fd 100644
--- a/libavcodec/wma.h
+++ b/libavcodec/wma.h
@@ -135,6 +135,8 @@ typedef struct WMACodecContext {
     float lsp_pow_m_table2[(1 << LSP_POW_BITS)];
     AVFloatDSPContext *fdsp;
 
+    int eof_done; /* decode flag to output remaining samples after EOF */
+
 #ifdef TRACE
     int frame_count;
 #endif /* TRACE */
diff --git a/libavcodec/wmadec.c b/libavcodec/wmadec.c
index cc67244344..9955aaa7d6 100644
--- a/libavcodec/wmadec.c
+++ b/libavcodec/wmadec.c
@@ -135,6 +135,8 @@ static av_cold int wma_decode_init(AVCodecContext *avctx)
 
     avctx->sample_fmt = AV_SAMPLE_FMT_FLTP;
 
+    avctx->internal->skip_samples = s->frame_len * 2;
+
     return 0;
 }
 
@@ -829,7 +831,20 @@ static int wma_decode_superframe(AVCodecContext *avctx, void *data,
     ff_tlog(avctx, "***decode_superframe:\n");
 
     if (buf_size == 0) {
+        if (s->eof_done)
+            return 0;
+
+        frame->nb_samples = s->frame_len;
+        if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
+            return ret;
+
+        for (i = 0; i < s->avctx->channels; i++)
+            memcpy(frame->extended_data[i], &s->frame_out[i][0],
+                   frame->nb_samples * sizeof(s->frame_out[i][0]));
+
         s->last_superframe_len = 0;
+        s->eof_done = 1;
+        *got_frame_ptr = 1;
         return 0;
     }
     if (buf_size < avctx->block_align) {
@@ -975,6 +990,9 @@ static av_cold void flush(AVCodecContext *avctx)
 
     s->last_bitoffset      =
     s->last_superframe_len = 0;
+
+    s->eof_done = 0;
+    avctx->internal->skip_samples = s->frame_len * 2;
 }
 
 #if CONFIG_WMAV1_DECODER
@@ -988,7 +1006,7 @@ const AVCodec ff_wmav1_decoder = {
     .close          = ff_wma_end,
     .decode         = wma_decode_superframe,
     .flush          = flush,
-    .capabilities   = AV_CODEC_CAP_DR1,
+    .capabilities   = AV_CODEC_CAP_DR1 | AV_CODEC_CAP_DELAY,
     .sample_fmts    = (const enum AVSampleFormat[]) { AV_SAMPLE_FMT_FLTP,
                                                       AV_SAMPLE_FMT_NONE },
     .caps_internal  = FF_CODEC_CAP_INIT_THREADSAFE | FF_CODEC_CAP_INIT_CLEANUP,
@@ -1005,7 +1023,7 @@ const AVCodec ff_wmav2_decoder = {
     .close          = ff_wma_end,
     .decode         = wma_decode_superframe,
     .flush          = flush,
-    .capabilities   = AV_CODEC_CAP_DR1,
+    .capabilities   = AV_CODEC_CAP_DR1 | AV_CODEC_CAP_DELAY,
     .sample_fmts    = (const enum AVSampleFormat[]) { AV_SAMPLE_FMT_FLTP,
                                                       AV_SAMPLE_FMT_NONE },
     .caps_internal  = FF_CODEC_CAP_INIT_THREADSAFE | FF_CODEC_CAP_INIT_CLEANUP,
diff --git a/tests/fate/wma.mak b/tests/fate/wma.mak
index bc530998e8..c13874ebfc 100644
--- a/tests/fate/wma.mak
+++ b/tests/fate/wma.mak
@@ -40,14 +40,14 @@ fate-wmavoice: $(FATE_WMAVOICE-yes)
 
 FATE_WMA_ENCODE-$(call ENCDEC, WMAV1, ASF) += fate-wmav1-encode
 fate-wmav1-encode: CMD = enc_dec_pcm asf wav s16le $(subst $(SAMPLES),$(TARGET_SAMPLES),$(REF)) -c:a wmav1 -b:a 128k
-fate-wmav1-encode: CMP_SHIFT = -8192
-fate-wmav1-encode: CMP_TARGET = 291.06
+fate-wmav1-encode: CMP_SHIFT = 8192
+fate-wmav1-encode: CMP_TARGET = 299.99
 fate-wmav1-encode: SIZE_TOLERANCE = 4632
 
 FATE_WMA_ENCODE-$(call ENCDEC, WMAV2, ASF) += fate-wmav2-encode
 fate-wmav2-encode: CMD = enc_dec_pcm asf wav s16le $(subst $(SAMPLES),$(TARGET_SAMPLES),$(REF)) -c:a wmav2 -b:a 128k
-fate-wmav2-encode: CMP_SHIFT = -8192
-fate-wmav2-encode: CMP_TARGET = 258.32
+fate-wmav2-encode: CMP_SHIFT = 8192
+fate-wmav2-encode: CMP_TARGET = 267.92
 fate-wmav2-encode: SIZE_TOLERANCE = 4632
 
 $(FATE_WMA_ENCODE-yes): CMP = stddev
diff --git a/tests/ref/fate/flcl1905 b/tests/ref/fate/flcl1905
index 5f5245ebcf..d702139db8 100644
--- a/tests/ref/fate/flcl1905
+++ b/tests/ref/fate/flcl1905
@@ -1,6 +1,4 @@
 packet|codec_type=audio|stream_index=0|pts=0|pts_time=0.000000|dts=0|dts_time=0.000000|duration=22528|duration_time=0.510839|size=4092|pos=56|flags=K_
-frame|media_type=audio|stream_index=0|key_frame=1|pts=0|pts_time=0.000000|pkt_dts=0|pkt_dts_time=0.000000|best_effort_timestamp=0|best_effort_timestamp_time=0.000000|pkt_duration=22528|pkt_duration_time=0.510839|pkt_pos=56|pkt_size=4092|sample_fmt=fltp|nb_samples=2048|channels=2|channel_layout=unknown
-frame|media_type=audio|stream_index=0|key_frame=1|pts=N/A|pts_time=N/A|pkt_dts=N/A|pkt_dts_time=N/A|best_effort_timestamp=N/A|best_effort_timestamp_time=N/A|pkt_duration=22528|pkt_duration_time=0.510839|pkt_pos=56|pkt_size=3720|sample_fmt=fltp|nb_samples=2048|channels=2|channel_layout=unknown
 frame|media_type=audio|stream_index=0|key_frame=1|pts=N/A|pts_time=N/A|pkt_dts=N/A|pkt_dts_time=N/A|best_effort_timestamp=N/A|best_effort_timestamp_time=N/A|pkt_duration=22528|pkt_duration_time=0.510839|pkt_pos=56|pkt_size=3348|sample_fmt=fltp|nb_samples=2048|channels=2|channel_layout=unknown
 frame|media_type=audio|stream_index=0|key_frame=1|pts=N/A|pts_time=N/A|pkt_dts=N/A|pkt_dts_time=N/A|best_effort_timestamp=N/A|best_effort_timestamp_time=N/A|pkt_duration=22528|pkt_duration_time=0.510839|pkt_pos=56|pkt_size=2976|sample_fmt=fltp|nb_samples=2048|channels=2|channel_layout=unknown
 frame|media_type=audio|stream_index=0|key_frame=1|pts=N/A|pts_time=N/A|pkt_dts=N/A|pkt_dts_time=N/A|best_effort_timestamp=N/A|best_effort_timestamp_time=N/A|pkt_duration=22528|pkt_duration_time=0.510839|pkt_pos=56|pkt_size=2604|sample_fmt=fltp|nb_samples=2048|channels=2|channel_layout=unknown
@@ -191,3 +189,4 @@ frame|media_type=audio|stream_index=0|key_frame=1|pts=N/A|pts_time=N/A|pkt_dts=N
 frame|media_type=audio|stream_index=0|key_frame=1|pts=N/A|pts_time=N/A|pkt_dts=N/A|pkt_dts_time=N/A|best_effort_timestamp=N/A|best_effort_timestamp_time=N/A|pkt_duration=22528|pkt_duration_time=0.510839|pkt_pos=61436|pkt_size=744|sample_fmt=fltp|nb_samples=2048|channels=2|channel_layout=unknown
 frame|media_type=audio|stream_index=0|key_frame=1|pts=N/A|pts_time=N/A|pkt_dts=N/A|pkt_dts_time=N/A|best_effort_timestamp=N/A|best_effort_timestamp_time=N/A|pkt_duration=22528|pkt_duration_time=0.510839|pkt_pos=61436|pkt_size=372|sample_fmt=fltp|nb_samples=2048|channels=2|channel_layout=unknown
 packet|codec_type=audio|stream_index=0|pts=360448|pts_time=8.173424|dts=360448|dts_time=8.173424|duration=44|duration_time=0.000998|size=8|pos=65528|flags=K_
+frame|media_type=audio|stream_index=0|key_frame=1|pts=N/A|pts_time=N/A|pkt_dts=N/A|pkt_dts_time=N/A|best_effort_timestamp=N/A|best_effort_timestamp_time=N/A|pkt_duration=N/A|pkt_duration_time=N/A|pkt_pos=N/A|pkt_size=0|sample_fmt=fltp|nb_samples=2048|channels=2|channel_layout=unknown