avcodec/v4l2m2m: allow lower minimum buffer values

There is no reason to enforce a high minimum. In the context
of streaming only a few output buffers and capture buffers
are even needed for continuous playback. This also helps
alleviate memory pressure when decoding 4K media.

Signed-off-by: Aman Karmani <aman@tmm1.net>

libavcodec/v4l2_m2m.h

@@ -38,7 +38,7 @@
 
 #define V4L_M2M_DEFAULT_OPTS \
     { "num_output_buffers", "Number of buffers in the output context",\
-        OFFSET(num_output_buffers), AV_OPT_TYPE_INT, { .i64 = 16 }, 6, INT_MAX, FLAGS }
+        OFFSET(num_output_buffers), AV_OPT_TYPE_INT, { .i64 = 16 }, 2, INT_MAX, FLAGS }
 
 typedef struct V4L2m2mContext {
     char devname[PATH_MAX];

libavcodec/v4l2_m2m_dec.c

@@ -226,7 +226,7 @@ static av_cold int v4l2_decode_close(AVCodecContext *avctx)
 static const AVOption options[] = {
     V4L_M2M_DEFAULT_OPTS,
     { "num_capture_buffers", "Number of buffers in the capture context",
-        OFFSET(num_capture_buffers), AV_OPT_TYPE_INT, {.i64 = 20}, 20, INT_MAX, FLAGS },
+        OFFSET(num_capture_buffers), AV_OPT_TYPE_INT, {.i64 = 20}, 2, INT_MAX, FLAGS },
     { NULL},
 };