afifo: fix request_samples on the last frame in certain cases

The current code can fail to return the last frame if it contains
exactly the requested number of samples.

Fixes the join filter test, which previously did not include the last
408 samples in most cases.

CC:libav-stable@libav.org
Signed-off-by: Diego Biurrun <diego@biurrun.de>

libavfilter/fifo.c

@@ -183,8 +183,25 @@ static int return_audio_frame(AVFilterContext *ctx)
         }
 
         while (s->out->nb_samples < s->allocated_samples) {
-            int len = FFMIN(s->allocated_samples - s->out->nb_samples,
-                            head->nb_samples);
+            int len;
+
+            if (!s->root.next) {
+                ret = ff_request_frame(ctx->inputs[0]);
+                if (ret == AVERROR_EOF) {
+                    av_samples_set_silence(s->out->extended_data,
+                                           s->out->nb_samples,
+                                           s->allocated_samples -
+                                           s->out->nb_samples,
+                                           nb_channels, link->format);
+                    s->out->nb_samples = s->allocated_samples;
+                    break;
+                } else if (ret < 0)
+                    return ret;
+            }
+            head = s->root.next->frame;
+
+            len = FFMIN(s->allocated_samples - s->out->nb_samples,
+                        head->nb_samples);
 
             av_samples_copy(s->out->extended_data, head->extended_data,
                             s->out->nb_samples, 0, len, nb_channels,
@@ -194,21 +211,6 @@ static int return_audio_frame(AVFilterContext *ctx)
             if (len == head->nb_samples) {
                 av_frame_free(&head);
                 queue_pop(s);
-
-                if (!s->root.next &&
-                    (ret = ff_request_frame(ctx->inputs[0])) < 0) {
-                    if (ret == AVERROR_EOF) {
-                        av_samples_set_silence(s->out->extended_data,
-                                               s->out->nb_samples,
-                                               s->allocated_samples -
-                                               s->out->nb_samples,
-                                               nb_channels, link->format);
-                        s->out->nb_samples = s->allocated_samples;
-                        break;
-                    }
-                    return ret;
-                }
-                head = s->root.next->frame;
             } else {
                 buffer_offset(link, head, len);
             }

tests/fate/filter-audio.mak

@@ -45,7 +45,7 @@ fate-filter-join: SRC2 = $(TARGET_PATH)/tests/data/asynth-44100-3.wav
 fate-filter-join: tests/data/asynth-44100-2.wav tests/data/asynth-44100-3.wav
 fate-filter-join: CMD = md5 -i $(SRC1) -i $(SRC2) -filter_complex join=channel_layout=5 -f s16le
 fate-filter-join: CMP = oneline
-fate-filter-join: REF = 38fa1b18b0c46d77df6f17bfc4f078dd
+fate-filter-join: REF = 409e66fc5ece4ddea4aa16bc47026bb0
 
 FATE_AFILTER-$(call FILTERDEMDECENCMUX, VOLUME, WAV, PCM_S16LE, PCM_S16LE, PCM_S16LE) += fate-filter-volume
 fate-filter-volume: SRC = $(TARGET_PATH)/tests/data/asynth-44100-2.wav