diff --git a/doc/bitstream_filters.texi b/doc/bitstream_filters.texi
index d10842ae47..46e4869f80 100644
--- a/doc/bitstream_filters.texi
+++ b/doc/bitstream_filters.texi
@@ -534,20 +534,62 @@ container. Can be used for fuzzing or testing error resilience/concealment.
 Parameters:
 @table @option
 @item amount
-A numeral string, whose value is related to how often output bytes will
-be modified. Therefore, values below or equal to 0 are forbidden, and
-the lower the more frequent bytes will be modified, with 1 meaning
-every byte is modified.
-@item dropamount
-A numeral string, whose value is related to how often packets will be dropped.
-Therefore, values below or equal to 0 are forbidden, and the lower the more
-frequent packets will be dropped, with 1 meaning every packet is dropped.
+Accepts an expression whose evaluation per-packet determines how often bytes in that
+packet will be modified. A value below 0 will result in a variable frequency.
+Default is 0 which results in no modification. However, if neither amount or drop is specified,
+amount will be set to @var{-1}. See below for accepted variables.
+@item drop, dropamount
+Accepts an expression evaluated per-packet whose value determines whether that packet is dropped.
+Evaluation to a positive value results in the packet being dropped. Evaluation to a negative
+value results in a variable chance of it being dropped, roughly inverse in proportion to the magnitude
+of the value. Default is 0 which results in no drops. See below for accepted variables.
 @end table
 
-The following example applies the modification to every byte but does not drop
-any packets.
+Both @code{amount} and @code{drop} accept expressions containing the following variables:
+
+@table @samp
+@item n
+The index of the packet, starting from zero.
+@item tb
+The timebase for packet timestamps.
+@item pts
+Packet presentation timestamp.
+@item dts
+Packet decoding timestamp.
+@item nopts
+Constant representing AV_NOPTS_VALUE.
+@item startpts
+First non-AV_NOPTS_VALUE PTS seen in the stream.
+@item startdts
+First non-AV_NOPTS_VALUE DTS seen in the stream.
+@item duration
+@itemx d
+Packet duration, in timebase units.
+@item pos
+Packet position in input; may be -1 when unknown or not set.
+@item size
+Packet size, in bytes.
+@item key
+Whether packet is marked as a keyframe.
+@item state
+A pseudo random integer, primarily derived from the content of packet payload.
+@end table
+
+@subsection Examples
+Apply modification to every byte but don't drop any packets.
+@example
+ffmpeg -i INPUT -c copy -bsf noise=1 output.mkv
+@end example
+
+Drop every video packet not marked as a keyframe after timestamp 30s but do not
+modify any of the remaining packets.
+@example
+ffmpeg -i INPUT -c copy -bsf:v noise=drop='gt(t\,30)*not(key)' output.mkv
+@end example
+
+Drop one second of audio every 10 seconds and add some random noise to the rest.
 @example
-ffmpeg -i INPUT -c copy -bsf noise[=1] output.mkv
+ffmpeg -i INPUT -c copy -bsf:a noise=amount=-1:drop='between(mod(t\,10)\,9\,10)' output.mkv
 @end example
 
 @section null
diff --git a/libavcodec/noise_bsf.c b/libavcodec/noise_bsf.c
index 6ebd369633..ab2221c5d1 100644
--- a/libavcodec/noise_bsf.c
+++ b/libavcodec/noise_bsf.c
@@ -23,55 +23,182 @@
 #include "bsf.h"
 #include "bsf_internal.h"
 
+#include "libavutil/avstring.h"
 #include "libavutil/log.h"
 #include "libavutil/opt.h"
+#include "libavutil/eval.h"
+
+static const char *const var_names[] = {
+    "n",                           /// packet index, starting from zero
+    "tb",                          /// timebase
+    "pts",                         /// packet presentation timestamp
+    "dts",                         /// packet decoding timestamp
+    "nopts",                       /// AV_NOPTS_VALUE
+    "startpts",                    /// first seen non-AV_NOPTS_VALUE packet timestamp
+    "startdts",                    /// first seen non-AV_NOPTS_VALUE packet timestamp
+    "duration", "d",               /// packet duration
+    "pos",                         /// original position of packet in its source
+    "size",                        /// packet size
+    "key" ,                        /// packet keyframe flag
+    "state",                       /// random-ish state
+    NULL
+};
+
+enum var_name {
+    VAR_N,
+    VAR_TB,
+    VAR_PTS,
+    VAR_DTS,
+    VAR_NOPTS,
+    VAR_STARTPTS,
+    VAR_STARTDTS,
+    VAR_DURATION, VAR_D,
+    VAR_POS,
+    VAR_SIZE,
+    VAR_KEY,
+    VAR_STATE,
+    VAR_VARS_NB
+};
 
 typedef struct NoiseContext {
     const AVClass *class;
-    int amount;
-    int dropamount;
+
+    char *amount_str;
+    char *drop_str;
+
+    AVExpr *amount_pexpr;
+    AVExpr *drop_pexpr;
+
+    double var_values[VAR_VARS_NB];
+
     unsigned int state;
+    unsigned int pkt_idx;
 } NoiseContext;
 
-static int noise(AVBSFContext *ctx, AVPacket *pkt)
+static int noise_init(AVBSFContext *ctx)
 {
     NoiseContext *s = ctx->priv_data;
-    int amount = s->amount > 0 ? s->amount : (s->state % 10001 + 1);
-    int i, ret;
+    int ret;
+
+    if (!s->amount_str) {
+        s->amount_str = !s->drop_str ? av_strdup("-1") : av_strdup("0");
+        if (!s->amount_str)
+            return AVERROR(ENOMEM);
+    }
+
+    ret = av_expr_parse(&s->amount_pexpr, s->amount_str,
+                        var_names, NULL, NULL, NULL, NULL, 0, ctx);
+    if (ret < 0) {
+        av_log(ctx, AV_LOG_ERROR, "Error in parsing expr for amount: %s\n", s->amount_str);
+        return ret;
+    }
+
+    if (s->drop_str) {
+        ret = av_expr_parse(&s->drop_pexpr, s->drop_str,
+                            var_names, NULL, NULL, NULL, NULL, 0, ctx);
+        if (ret < 0) {
+            av_log(ctx, AV_LOG_ERROR, "Error in parsing expr for drop: %s\n", s->drop_str);
+            return ret;
+        }
+    }
+
+    s->var_values[VAR_TB]       = ctx->time_base_out.den ? av_q2d(ctx->time_base_out) : 0;
+    s->var_values[VAR_NOPTS]    = AV_NOPTS_VALUE;
+    s->var_values[VAR_STARTPTS] = AV_NOPTS_VALUE;
+    s->var_values[VAR_STARTDTS] = AV_NOPTS_VALUE;
+    s->var_values[VAR_STATE] = 0;
+
+    return 0;
+}
 
-    if (amount <= 0)
-        return AVERROR(EINVAL);
+static int noise(AVBSFContext *ctx, AVPacket *pkt)
+{
+    NoiseContext *s = ctx->priv_data;
+    int i, ret, amount, drop;
+    double res;
 
     ret = ff_bsf_get_packet_ref(ctx, pkt);
     if (ret < 0)
         return ret;
 
-    if (s->dropamount > 0 && s->state % s->dropamount == 0) {
-        s->state++;
+    s->var_values[VAR_N]           = s->pkt_idx++;
+    s->var_values[VAR_PTS]         = pkt->pts;
+    s->var_values[VAR_DTS]         = pkt->dts;
+    s->var_values[VAR_DURATION]    =
+    s->var_values[VAR_D]           = pkt->duration;
+    s->var_values[VAR_SIZE]        = pkt->size;
+    s->var_values[VAR_KEY]         = !!(pkt->flags & AV_PKT_FLAG_KEY);
+    s->var_values[VAR_POS]         = pkt->pos;
+
+    if (s->var_values[VAR_STARTPTS] == AV_NOPTS_VALUE)
+        s->var_values[VAR_STARTPTS] = pkt->pts;
+
+    if (s->var_values[VAR_STARTDTS] == AV_NOPTS_VALUE)
+        s->var_values[VAR_STARTDTS] = pkt->dts;
+
+    res = av_expr_eval(s->amount_pexpr, s->var_values, NULL);
+
+    if (isnan(res))
+        amount = 0;
+    else if (res < 0)
+        amount = (s->state % 10001 + 1);
+    else
+        amount = (int)res;
+
+    if (s->drop_str) {
+        res = av_expr_eval(s->drop_pexpr, s->var_values, NULL);
+
+        if (isnan(res))
+            drop = 0;
+        else if (res < 0)
+            drop = !(s->state % FFABS((int)res));
+        else
+            drop = !!res;
+    }
+
+    av_log(ctx, AV_LOG_VERBOSE, "Stream #%d packet %d pts %"PRId64" - amount %d drop %d\n",
+           pkt->stream_index, (unsigned int)s->var_values[VAR_N], pkt->pts, amount, drop);
+
+    if (s->drop_str && drop) {
+        s->var_values[VAR_STATE] = ++s->state;
         av_packet_unref(pkt);
         return AVERROR(EAGAIN);
     }
 
-    ret = av_packet_make_writable(pkt);
-    if (ret < 0) {
-        av_packet_unref(pkt);
-        return ret;
+    if (amount) {
+        ret = av_packet_make_writable(pkt);
+        if (ret < 0) {
+            av_packet_unref(pkt);
+            return ret;
+        }
     }
 
     for (i = 0; i < pkt->size; i++) {
         s->state += pkt->data[i] + 1;
-        if (s->state % amount == 0)
+        if (amount && s->state % amount == 0)
             pkt->data[i] = s->state;
     }
 
+    s->var_values[VAR_STATE] = s->state;
+
     return 0;
 }
 
+static void noise_close(AVBSFContext *bsf)
+{
+    NoiseContext *s = ctx->priv_data;
+
+    av_expr_free(s->amount_pexpr);
+    av_expr_free(s->drop_pexpr);
+    s->amount_pexpr = s->drop_pexpr = NULL;
+}
+
 #define OFFSET(x) offsetof(NoiseContext, x)
 #define FLAGS (AV_OPT_FLAG_VIDEO_PARAM|AV_OPT_FLAG_AUDIO_PARAM|AV_OPT_FLAG_BSF_PARAM)
 static const AVOption options[] = {
-    { "amount", NULL, OFFSET(amount), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, INT_MAX, FLAGS },
-    { "dropamount", NULL, OFFSET(dropamount), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, INT_MAX, FLAGS },
+    { "amount",     NULL, OFFSET(amount_str),     AV_OPT_TYPE_STRING, { .str = NULL }, 0, 0, FLAGS },
+    { "drop",       NULL, OFFSET(drop_str),       AV_OPT_TYPE_STRING, { .str = NULL }, 0, 0, FLAGS },
+    { "dropamount", NULL, OFFSET(drop_str),       AV_OPT_TYPE_STRING, { .str = NULL }, 0, 0, FLAGS },
     { NULL },
 };
 
@@ -86,5 +213,7 @@ const AVBitStreamFilter ff_noise_bsf = {
     .name           = "noise",
     .priv_data_size = sizeof(NoiseContext),
     .priv_class     = &noise_class,
+    .init           = noise_init,
+    .close          = noise_close,
     .filter         = noise,
 };
diff --git a/tests/fate/matroska.mak b/tests/fate/matroska.mak
index ca7193a055..b57765280a 100644
--- a/tests/fate/matroska.mak
+++ b/tests/fate/matroska.mak
@@ -88,7 +88,7 @@ FATE_MATROSKA_FFMPEG_FFPROBE-$(call ALLYES, FILE_PROTOCOL MXF_DEMUXER        \
                                             MATROSKA_MUXER MATROSKA_DEMUXER  \
                                             FRAMECRC_MUXER PIPE_PROTOCOL)    \
                                += fate-matroska-mastering-display-metadata
-fate-matroska-mastering-display-metadata: CMD = transcode mxf $(TARGET_SAMPLES)/mxf/Meridian-Apple_ProResProxy-HDR10.mxf matroska "-map 0 -map 0:0 -c:v:0 copy -c:v:1 ffv1 -c:a:0 copy -bsf:a:0 noise=amount=3 -filter:a:1 aresample -c:a:1 pcm_s16be -bsf:a:1 noise=dropamount=4" "-map 0 -c copy" "" "-show_entries stream_side_data_list:stream=index,codec_name"
+fate-matroska-mastering-display-metadata: CMD = transcode mxf $(TARGET_SAMPLES)/mxf/Meridian-Apple_ProResProxy-HDR10.mxf matroska "-map 0 -map 0:0 -c:v:0 copy -c:v:1 ffv1 -c:a:0 copy -bsf:a:0 noise=amount=3 -filter:a:1 aresample -c:a:1 pcm_s16be -bsf:a:1 noise=amount=-1:dropamount=-4" "-map 0 -c copy" "" "-show_entries stream_side_data_list:stream=index,codec_name"
 
 # This test tests remuxing annex B H.264 into Matroska. It also tests writing
 # the correct interlaced flags and overriding the sample aspect ratio, leading
