avisynth: Use av_packet_from_data instead of av_new_packet

If the audio changes from 9eac7c43 were merged as they were, this
would cause scripts with both video+audio to fail with a lot of
audio decoding errors (the video would be fine). Scripts with
only one of either video or audio were unaffected. Additionally,
the av_packet changes in general caused seeking to break.

Using av_packet_from_data allows video+audio scripts to work as
expected, without audio decoding errors.  It also fixes seeking.
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/avisynth.c

@@ -421,7 +421,7 @@ static int avisynth_read_packet_video(AVFormatContext *s, AVPacket *pkt,
     AVS_VideoFrame *frame;
     unsigned char *dst_p;
     const unsigned char *src_p;
-    int n, i, plane, rowsize, planeheight, pitch, bits;
+    int n, i, plane, rowsize, planeheight, pitch, bits, ret;
     const char *error;
 
     if (avs->curr_frame >= avs->vi->num_frames)
@@ -460,9 +460,15 @@ static int avisynth_read_packet_video(AVFormatContext *s, AVPacket *pkt,
     if (!pkt->size)
         return AVERROR_UNKNOWN;
 
-    if (av_new_packet(pkt, pkt->size) < 0)
+    pkt->data = av_malloc(pkt->size);
+    if (!pkt->data)
         return AVERROR(ENOMEM);
 
+    if ((ret = av_packet_from_data(pkt, pkt->data, pkt->size)) < 0) {
+        av_packet_unref(pkt);
+        return ret;
+    }
+
     frame = avs_library.avs_get_frame(avs->clip, n);
     error = avs_library.avs_clip_get_error(avs->clip);
     if (error) {
@@ -511,7 +517,7 @@ static int avisynth_read_packet_audio(AVFormatContext *s, AVPacket *pkt,
 {
     AviSynthContext *avs = s->priv_data;
     AVRational fps, samplerate;
-    int samples;
+    int samples, ret;
     int64_t n;
     const char *error;
 
@@ -558,9 +564,15 @@ static int avisynth_read_packet_audio(AVFormatContext *s, AVPacket *pkt,
     if (!pkt->size)
         return AVERROR_UNKNOWN;
 
-    if (av_new_packet(pkt, pkt->size) < 0)
+    pkt->data = av_malloc(pkt->size);
+    if (!pkt->data)
         return AVERROR(ENOMEM);
 
+    if ((ret = av_packet_from_data(pkt, pkt->data, pkt->size)) < 0) {
+        av_packet_unref(pkt);
+        return ret;
+    }
+
     avs_library.avs_get_audio(avs->clip, pkt->data, n, samples);
     error = avs_library.avs_clip_get_error(avs->clip);
     if (error) {