From 048ff837f7377a8ad05a2b0012eb8f2639a0a049 Mon Sep 17 00:00:00 2001
From: Romain Vimont <rom@rom1v.com>
Date: Sat, 25 Feb 2023 16:19:58 +0100
Subject: [PATCH] Pass AVCodecContext to frame sinks

Frame consumers may need details about the frame format.
---
 app/src/decoder.c          | 11 ++++++++---
 app/src/screen.c           |  5 ++++-
 app/src/trait/frame_sink.h |  3 ++-
 app/src/v4l2_sink.c        |  4 +++-
 4 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/app/src/decoder.c b/app/src/decoder.c
index d750253c..46c95929 100644
--- a/app/src/decoder.c
+++ b/app/src/decoder.c
@@ -25,10 +25,10 @@ sc_decoder_close_sinks(struct sc_decoder *decoder) {
 }
 
 static bool
-sc_decoder_open_sinks(struct sc_decoder *decoder) {
+sc_decoder_open_sinks(struct sc_decoder *decoder, const AVCodecContext *ctx) {
     for (unsigned i = 0; i < decoder->sink_count; ++i) {
         struct sc_frame_sink *sink = decoder->sinks[i];
-        if (!sink->ops->open(sink)) {
+        if (!sink->ops->open(sink, ctx)) {
             sc_decoder_close_first_sinks(decoder, i);
             return false;
         }
@@ -47,6 +47,11 @@ sc_decoder_open(struct sc_decoder *decoder, const AVCodec *codec) {
 
     decoder->codec_ctx->flags |= AV_CODEC_FLAG_LOW_DELAY;
 
+    if (codec->type == AVMEDIA_TYPE_VIDEO) {
+        // Only YUV 4:2:0 is supported, hardcode it
+        decoder->codec_ctx->pix_fmt = AV_PIX_FMT_YUV420P;
+    }
+
     if (avcodec_open2(decoder->codec_ctx, codec, NULL) < 0) {
         LOGE("Decoder '%s': could not open codec", decoder->name);
         avcodec_free_context(&decoder->codec_ctx);
@@ -61,7 +66,7 @@ sc_decoder_open(struct sc_decoder *decoder, const AVCodec *codec) {
         return false;
     }
 
-    if (!sc_decoder_open_sinks(decoder)) {
+    if (!sc_decoder_open_sinks(decoder, decoder->codec_ctx)) {
         av_frame_free(&decoder->frame);
         avcodec_close(decoder->codec_ctx);
         avcodec_free_context(&decoder->codec_ctx);
diff --git a/app/src/screen.c b/app/src/screen.c
index 425ba2c3..5dd45c26 100644
--- a/app/src/screen.c
+++ b/app/src/screen.c
@@ -330,7 +330,10 @@ event_watcher(void *data, SDL_Event *event) {
 #endif
 
 static bool
-sc_screen_frame_sink_open(struct sc_frame_sink *sink) {
+sc_screen_frame_sink_open(struct sc_frame_sink *sink,
+                          const AVCodecContext *ctx) {
+    assert(ctx->pix_fmt == AV_PIX_FMT_YUV420P);
+
     struct sc_screen *screen = DOWNCAST(sink);
     (void) screen;
 #ifndef NDEBUG
diff --git a/app/src/trait/frame_sink.h b/app/src/trait/frame_sink.h
index 0214ab3e..30bf0d37 100644
--- a/app/src/trait/frame_sink.h
+++ b/app/src/trait/frame_sink.h
@@ -5,6 +5,7 @@
 
 #include <assert.h>
 #include <stdbool.h>
+#include <libavcodec/avcodec.h>
 
 typedef struct AVFrame AVFrame;
 
@@ -18,7 +19,7 @@ struct sc_frame_sink {
 };
 
 struct sc_frame_sink_ops {
-    bool (*open)(struct sc_frame_sink *sink);
+    bool (*open)(struct sc_frame_sink *sink, const AVCodecContext *ctx);
     void (*close)(struct sc_frame_sink *sink);
     bool (*push)(struct sc_frame_sink *sink, const AVFrame *frame);
 };
diff --git a/app/src/v4l2_sink.c b/app/src/v4l2_sink.c
index 9a0011f2..15ca7c60 100644
--- a/app/src/v4l2_sink.c
+++ b/app/src/v4l2_sink.c
@@ -156,7 +156,9 @@ sc_video_buffer_on_new_frame(struct sc_video_buffer *vb, bool previous_skipped,
 }
 
 static bool
-sc_v4l2_sink_open(struct sc_v4l2_sink *vs) {
+sc_v4l2_sink_open(struct sc_v4l2_sink *vs, const AVCodecContext *ctx) {
+    assert(ctx->pix_fmt == AV_PIX_FMT_YUV420P);
+
     static const struct sc_video_buffer_callbacks cbs = {
         .on_new_frame = sc_video_buffer_on_new_frame,
     };