From 55d414829c601ec5482be61aa327c22f0f602fe1 Mon Sep 17 00:00:00 2001
From: Paul B Mahol <onemda@gmail.com>
Date: Thu, 7 Apr 2022 09:35:57 +0200
Subject: [PATCH] avfilter/af_ladspa: fix pts compensation if number of samples
 per frame is lower than latency

---
 libavfilter/af_ladspa.c | 27 ++++++++++++++++++++++++---
 1 file changed, 24 insertions(+), 3 deletions(-)

diff --git a/libavfilter/af_ladspa.c b/libavfilter/af_ladspa.c
index bf51b372ff..1c3ede2ee2 100644
--- a/libavfilter/af_ladspa.c
+++ b/libavfilter/af_ladspa.c
@@ -29,11 +29,17 @@
 #include "libavutil/avassert.h"
 #include "libavutil/avstring.h"
 #include "libavutil/channel_layout.h"
+#include "libavutil/fifo.h"
 #include "libavutil/opt.h"
 #include "audio.h"
 #include "avfilter.h"
 #include "internal.h"
 
+typedef struct MetaItem {
+    int64_t pts;
+    int nb_samples;
+} MetaItem;
+
 typedef struct LADSPAContext {
     const AVClass *class;
     char *dl_name;
@@ -69,6 +75,8 @@ typedef struct LADSPAContext {
     int in_trim;
     int out_pad;
     int latency;
+
+    AVFifo *fifo;
 } LADSPAContext;
 
 #define OFFSET(x) offsetof(LADSPAContext, x)
@@ -169,6 +177,7 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *in)
     int64_t out_duration;
     int64_t in_duration;
     int64_t in_pts;
+    MetaItem meta;
 
     av_assert0(in->ch_layout.nb_channels == (s->nb_inputs * s->nb_handles));
 
@@ -210,8 +219,9 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *in)
     for (i = 0; i < s->nb_outputcontrols; i++)
         print_ctl_info(ctx, AV_LOG_VERBOSE, s, i, s->ocmap, s->octlv, 1);
 
-    in_duration = av_rescale_q(in->nb_samples,  inlink->time_base, av_make_q(1,  in->sample_rate));
-    in_pts = in->pts;
+    meta = (MetaItem){ in->pts, in->nb_samples };
+    av_fifo_write(s->fifo, &meta, 1);
+
     if (out != in)
         av_frame_free(&in);
 
@@ -235,9 +245,14 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *in)
         out->nb_samples = new_out_samples;
     }
 
+    av_fifo_read(s->fifo, &meta, 1);
+
     out_duration = av_rescale_q(out->nb_samples, inlink->time_base, av_make_q(1, out->sample_rate));
+    in_duration  = av_rescale_q(meta.nb_samples, inlink->time_base, av_make_q(1, out->sample_rate));
+    in_pts       = meta.pts;
+
     if (s->next_out_pts != AV_NOPTS_VALUE && out->pts != s->next_out_pts &&
-        s->next_in_pts  != AV_NOPTS_VALUE && out->pts == s->next_in_pts) {
+        s->next_in_pts  != AV_NOPTS_VALUE && in_pts   == s->next_in_pts) {
         out->pts = s->next_out_pts;
     } else {
         out->pts = in_pts;
@@ -676,6 +691,10 @@ static av_cold int init(AVFilterContext *ctx)
     s->next_out_pts = AV_NOPTS_VALUE;
     s->next_in_pts  = AV_NOPTS_VALUE;
 
+    s->fifo = av_fifo_alloc2(8, sizeof(MetaItem), AV_FIFO_FLAG_AUTO_GROW);
+    if (!s->fifo)
+        return AVERROR(ENOMEM);
+
     return 0;
 }
 
@@ -775,6 +794,8 @@ static av_cold void uninit(AVFilterContext *ctx)
     av_freep(&s->octlv);
     av_freep(&s->handles);
     av_freep(&s->ctl_needs_value);
+
+    av_fifo_freep2(&s->fifo);
 }
 
 static int process_command(AVFilterContext *ctx, const char *cmd, const char *args,