Use AV_PIX_FMT_FLAG_ALPHA for detecting transparency where nb_components was used

Temporarily keep the old method for ffmpeg_filters.c choose_pix_fmt and
avfiltergraph.c pick_format() until a paletted pixel format without alpha is
introduced.
Signed-off-by: Marton Balint <cus@passwd.hu>

fftools/ffmpeg_filter.c

@@ -65,6 +65,7 @@ enum AVPixelFormat choose_pixel_fmt(AVStream *st, AVCodecContext *enc_ctx, AVCod
     if (codec && codec->pix_fmts) {
         const enum AVPixelFormat *p = codec->pix_fmts;
         const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(target);
+        //FIXME: This should check for AV_PIX_FMT_FLAG_ALPHA after PAL8 pixel format without alpha is implemented
         int has_alpha = desc ? desc->nb_components % 2 == 0 : 0;
         enum AVPixelFormat best= AV_PIX_FMT_NONE;
 

libavcodec/ffv1enc.c

@@ -624,7 +624,7 @@ FF_ENABLE_DEPRECATION_WARNINGS
     case AV_PIX_FMT_YUVA420P:
         s->chroma_planes = desc->nb_components < 3 ? 0 : 1;
         s->colorspace = 0;
-        s->transparency = desc->nb_components == 4 || desc->nb_components == 2;
+        s->transparency = !!(desc->flags & AV_PIX_FMT_FLAG_ALPHA);
         if (!avctx->bits_per_raw_sample && !s->bits_per_raw_sample)
             s->bits_per_raw_sample = 8;
         else if (!s->bits_per_raw_sample)
@@ -676,7 +676,7 @@ FF_ENABLE_DEPRECATION_WARNINGS
             s->bits_per_raw_sample = 16;
         else if (!s->bits_per_raw_sample)
             s->bits_per_raw_sample = avctx->bits_per_raw_sample;
-        s->transparency = desc->nb_components == 4 || desc->nb_components == 2;
+        s->transparency = !!(desc->flags & AV_PIX_FMT_FLAG_ALPHA);
         s->colorspace = 1;
         s->chroma_planes = 1;
         if (s->bits_per_raw_sample >= 16) {

libavfilter/avfiltergraph.c

@@ -679,6 +679,7 @@ static int pick_format(AVFilterLink *link, AVFilterLink *ref)
 
     if (link->type == AVMEDIA_TYPE_VIDEO) {
         if(ref && ref->type == AVMEDIA_TYPE_VIDEO){
+            //FIXME: This should check for AV_PIX_FMT_FLAG_ALPHA after PAL8 pixel format without alpha is implemented
             int has_alpha= av_pix_fmt_desc_get(ref->format)->nb_components % 2 == 0;
             enum AVPixelFormat best= AV_PIX_FMT_NONE;
             int i;

libavutil/pixdesc.c

@@ -2482,7 +2482,7 @@ enum AVPixelFormat av_pix_fmt_swap_endianness(enum AVPixelFormat pix_fmt)
 #define FF_COLOR_XYZ      4
 
 #define pixdesc_has_alpha(pixdesc) \
-    ((pixdesc)->nb_components == 2 || (pixdesc)->nb_components == 4 || (pixdesc)->flags & AV_PIX_FMT_FLAG_PAL)
+    ((pixdesc)->flags & AV_PIX_FMT_FLAG_ALPHA)
 
 
 static int get_color_type(const AVPixFmtDescriptor *desc) {