[FFmpeg-devel] [PATCH] avfilter/acrossfade: allow skipping fade on inputs

[Gyan]

On 23-01-2019 07:40 PM, Paul B Mahol wrote:
> On 1/23/19, Gyan <ffmpeg at gyani.pro> wrote:
>>
>> On 23-01-2019 03:00 PM, Paul B Mahol wrote:
>>> On 1/23/19, Gyan <ffmpeg at gyani.pro> wrote:
>>> Why? afade needs change too.
>> If a user doesn't want to apply fade, then they can simply not add afade
>> filter. This change is meant for users who want to combine two audio
>> streams with overlap but don't want to apply fade to audio during overlap.
>>
> I do not like such reasoning, also you changed afade too with this approach.

That was to prevent an integer value of nb_curves-1 from being accepted.

Anyway, revised patch attached, although I don't see how afade=c=nofade 
   is useful.

Gyan
-------------- next part --------------
From e8ee422323eabad02ac4c2385c8d5a5997f6cab8 Mon Sep 17 00:00:00 2001
From: Gyan Doshi <ffmpeg at gyani.pro>
Date: Wed, 23 Jan 2019 13:35:23 +0530
Subject: [PATCH v2] avfilter/afade+acrossfade: allow skipping fade on inputs

New fade curve value 'nofade' passes audio samples as-is.
Primarily useful in carrying out acrossfade without fades.
---
 doc/filters.texi       | 2 ++
 libavfilter/af_afade.c | 7 ++++++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/doc/filters.texi b/doc/filters.texi
index d06dfe089f..fc98323af0 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -958,6 +958,8 @@ select double-exponential seat
 select double-exponential sigmoid
 @item losi
 select logistic sigmoid
+ at item nofade
+no fade applied
 @end table
 @end table
 
diff --git a/libavfilter/af_afade.c b/libavfilter/af_afade.c
index 751db7da4d..195fb65ab5 100644
--- a/libavfilter/af_afade.c
+++ b/libavfilter/af_afade.c
@@ -51,7 +51,7 @@ typedef struct AudioFadeContext {
                               int curve0, int curve1);
 } AudioFadeContext;
 
-enum CurveType { TRI, QSIN, ESIN, HSIN, LOG, IPAR, QUA, CUB, SQU, CBR, PAR, EXP, IQSIN, IHSIN, DESE, DESI, LOSI, NB_CURVES };
+enum CurveType { TRI, QSIN, ESIN, HSIN, LOG, IPAR, QUA, CUB, SQU, CBR, PAR, EXP, IQSIN, IHSIN, DESE, DESI, LOSI, NONE, NB_CURVES };
 
 #define OFFSET(x) offsetof(AudioFadeContext, x)
 #define FLAGS AV_OPT_FLAG_AUDIO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
@@ -153,6 +153,9 @@ static double fade_gain(int curve, int64_t index, int64_t range)
                    gain = (A - B) / (C - B);
                }
         break;
+    case NONE:
+        gain = 1.0;
+        break;
     }
 
     return gain;
@@ -260,6 +263,7 @@ static const AVOption afade_options[] = {
     { "dese",         "double-exponential seat",                     0,                    AV_OPT_TYPE_CONST,  {.i64 = DESE }, 0, 0, FLAGS, "curve" },
     { "desi",         "double-exponential sigmoid",                  0,                    AV_OPT_TYPE_CONST,  {.i64 = DESI }, 0, 0, FLAGS, "curve" },
     { "losi",         "logistic sigmoid",                            0,                    AV_OPT_TYPE_CONST,  {.i64 = LOSI }, 0, 0, FLAGS, "curve" },
+    { "nofade",       "no fade; keep audio as-is",                   0,                    AV_OPT_TYPE_CONST,  {.i64 = NONE }, 0, 0, FLAGS, "curve" },
     { NULL }
 };
 
@@ -380,6 +384,7 @@ static const AVOption acrossfade_options[] = {
     {     "dese",     "double-exponential seat",                       0,                    AV_OPT_TYPE_CONST,  {.i64 = DESE }, 0, 0, FLAGS, "curve" },
     {     "desi",     "double-exponential sigmoid",                    0,                    AV_OPT_TYPE_CONST,  {.i64 = DESI }, 0, 0, FLAGS, "curve" },
     {     "losi",     "logistic sigmoid",                              0,                    AV_OPT_TYPE_CONST,  {.i64 = LOSI }, 0, 0, FLAGS, "curve" },
+    {     "nofade",   "no fade; keep audio as-is",                     0,                    AV_OPT_TYPE_CONST,  {.i64 = NONE }, 0, 0, FLAGS, "curve" },
     { "curve2",       "set fade curve type for 2nd stream",            OFFSET(curve2),       AV_OPT_TYPE_INT,    {.i64 = TRI  }, 0, NB_CURVES - 1, FLAGS, "curve" },
     { "c2",           "set fade curve type for 2nd stream",            OFFSET(curve2),       AV_OPT_TYPE_INT,    {.i64 = TRI  }, 0, NB_CURVES - 1, FLAGS, "curve" },
     { NULL }
-- 
2.19.2