From a6ec2aa1ffa32b7a670c64e81dd29af20a23036c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Micha=C5=82=20=C5=9Aled=C5=BA?= <michalsledz34@gmail.com>
Date: Thu, 8 Aug 2024 10:19:13 +0200
Subject: [PATCH] Handle decoder only frames

---
 c_src/xav/xav_decoder.c | 6 ++++++
 lib/decoder.ex          | 9 ++++++++-
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/c_src/xav/xav_decoder.c b/c_src/xav/xav_decoder.c
index 8332a72..101069f 100644
--- a/c_src/xav/xav_decoder.c
+++ b/c_src/xav/xav_decoder.c
@@ -102,8 +102,14 @@ ERL_NIF_TERM decode(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[]) {
       decoder_decode(xav_decoder->decoder, xav_decoder->decoder->pkt, xav_decoder->decoder->frame);
   if (ret == -2) {
     return xav_nif_error(env, "no_keyframe");
+  } else if (ret == AVERROR(EAGAIN)) {
+    // Some frames are meant for decoder only
+    // and they don't include actual video samples.
+    decoder_free_frame(xav_decoder->decoder);
+    return enif_make_atom(env, "ok");
   } else if (ret != 0) {
     return xav_nif_raise(env, "failed_to_decode");
+    AVERROR(EAGAIN);
   }
 
   // convert
diff --git a/lib/decoder.ex b/lib/decoder.ex
index e6be460..7693ef6 100644
--- a/lib/decoder.ex
+++ b/lib/decoder.ex
@@ -63,14 +63,21 @@ defmodule Xav.Decoder do
 
   @doc """
   Decodes an audio/video frame.
+
+  Some frames are meant for decoder only and might not
+  contain actual video samples.
+  In such cases, `:ok` term is returned.
   """
   @spec decode(t(), binary(), pts: integer(), dts: integer()) ::
-          {:ok, Xav.Frame.t()} | {:error, atom()}
+          :ok | {:ok, Xav.Frame.t()} | {:error, atom()}
   def decode(decoder, data, opts \\ []) do
     pts = opts[:pts] || 0
     dts = opts[:dts] || 0
 
     case Xav.Decoder.NIF.decode(decoder, data, pts, dts) do
+      :ok ->
+        :ok
+
       {:ok, {data, format, width, height, pts}} ->
         {:ok, Xav.Frame.new(data, format, width, height, pts)}