audio/owntone: Circumvent ffmpeg 6 ALAC encoding problem

owntone/owntone-server#1640

audio/owntone/Makefile

@@ -1,6 +1,6 @@
 PORTNAME=	owntone
 DISTVERSION=	28.5
-PORTREVISION=	4
+PORTREVISION=	5
 CATEGORIES=	audio
 MASTER_SITES=	https://github.com/owntone/owntone-server/releases/download/${DISTVERSION}/
 

audio/owntone/files/patch-src_transcode.c

@@ -0,0 +1,43 @@
+From 941fab9023f0af19f178771effd2a73865e849ba Mon Sep 17 00:00:00 2001
+From: ejurgensen <espenjurgensen@gmail.com>
+Date: Thu, 17 Aug 2023 23:09:41 +0200
+Subject: [PATCH] [xcode] Circumvent ffmpeg 6 ALAC encoding problem
+
+The default ffmpeg ALAC encoder, "alac", requires fixed frames of size 4096,
+but the Airplay 2 implementation feeds it with frames of size 352. Before
+ffmpeg 6 this worked, but not any more. Seems a frame size check has been
+added.
+
+This commit doesn't fix this, but circumvents the ffmpeg error by modifying the
+frame size that ffmpeg checks.
+
+Fixes issue #1640
+
+--- src/transcode.c.orig	2022-01-29 16:41:27 UTC
++++ src/transcode.c
+@@ -42,6 +42,8 @@
+ #include "misc.h"
+ #include "transcode.h"
+
++#define USE_ALAC_FRAME_SIZE_HACK (LIBAVCODEC_VERSION_MAJOR > 59) || ((LIBAVCODEC_VERSION_MAJOR == 59) && (LIBAVCODEC_VERSION_MINOR > 31))
++
+ // Interval between ICY metadata checks for streams, in seconds
+ #define METADATA_ICY_INTERVAL 5
+ // Maximum number of streams in a file that we will accept
+@@ -506,6 +508,16 @@ stream_add(struct encode_ctx *ctx, struct stream_ctx *
+       avcodec_free_context(&s->codec);
+       return -1;
+     }
++
++  // airplay.c "misuses" the ffmpeg alac encoder in that it pushes frames with
++  // 352 samples even though the encoder wants 4096 (and doesn't have variable
++  // frame capability). This worked with no issues until ffmpeg 6, where it
++  // seems a frame size check was added. The below circumvents the check, but is
++  // dirty because we shouldn't be writing to this data element.
++#if USE_ALAC_FRAME_SIZE_HACK
++  if (codec_id == AV_CODEC_ID_ALAC)
++    s->codec->frame_size = 352;
++#endif
+ 
+   // Copy the codec parameters we just set to the stream, so the muxer knows them
+   ret = avcodec_parameters_from_context(s->stream->codecpar, s->codec);