[FFmpeg-devel] [PATCH v2 4/5] fftools/ffmpeg: flush and recreate encoder instance if resolution changes

[Linjie Fu]

Add recreate_encoder_instance() function.

If resolution changing is allowed, discard AV_CODEC_FLAG_GLOBAL_HEADER
even if the avformat/container declares AVFMT_GLOBALHEADER flag. Place
header information in every keyframe instead of single global header.

Signed-off-by: Linjie Fu <linjie.fu at intel.com>
---
Should be squashed with:
https://patchwork.ffmpeg.org/project/ffmpeg/list/?series=1434

 fftools/ffmpeg.c     | 40 ++++++++++++++++++++++++++++++++++++++++
 fftools/ffmpeg_opt.c |  2 +-
 2 files changed, 41 insertions(+), 1 deletion(-)

diff --git a/fftools/ffmpeg.c b/fftools/ffmpeg.c
index 5859781..86562c9 100644
--- a/fftools/ffmpeg.c
+++ b/fftools/ffmpeg.c
@@ -130,6 +130,7 @@ static void do_video_stats(OutputStream *ost, int frame_size);
 static BenchmarkTimeStamps get_benchmark_time_stamps(void);
 static int64_t getmaxrss(void);
 static int ifilter_has_all_input_formats(FilterGraph *fg);
+static void flush_encoders(void);
 
 static int run_as_daemon  = 0;
 static int nb_frames_dup = 0;
@@ -1039,6 +1040,37 @@ static void do_subtitle_out(OutputFile *of,
     }
 }
 
+static int recreate_encoder_instance(OutputStream *ost,
+                                     int width, int height)
+{
+    AVCodec *encoder = ost->enc_ctx->codec;
+    AVRational time_base = ost->enc_ctx->time_base;
+    int ret;
+
+    avcodec_free_context(&ost->enc_ctx);
+
+    ost->enc_ctx = avcodec_alloc_context3(encoder);
+    if (!ost->enc_ctx)
+        return AVERROR(ENOMEM);
+
+    ost->st->codecpar->width  = width;
+    ost->st->codecpar->height = height;
+
+    if (ret = avcodec_parameters_to_context(ost->enc_ctx, ost->st->codecpar) < 0)
+        return ret;
+
+    ost->enc_ctx->time_base = time_base;
+
+    if (ret = avcodec_open2(ost->enc_ctx, encoder, &ost->encoder_opts) < 0) {
+        av_log(NULL, AV_LOG_ERROR, "Error while re-opening encoder for output stream #%d:%d - "
+               "maybe incorrect parameters such as bit_rate, rate, width or height.\n",
+               ost->file_index, ost->index);
+        return ret;
+    }
+
+    return 0;
+}
+
 static void do_video_out(OutputFile *of,
                          OutputStream *ost,
                          AVFrame *next_picture,
@@ -1058,11 +1090,19 @@ static void do_video_out(OutputFile *of,
 
     if (next_picture && (enc->width != next_picture->width ||
                          enc->height != next_picture->height)) {
+        flush_encoders();
+        avcodec_flush_buffers(enc);
+
         if (!(enc->codec->capabilities & AV_CODEC_CAP_VARIABLE_DIMENSIONS)) {
             av_log(NULL, AV_LOG_ERROR, "Variable dimension encoding "
                             "is not supported by %s.\n", enc->codec->name);
             goto error;
         }
+
+        if (recreate_encoder_instance(ost, next_picture->width, next_picture->height) < 0)
+            goto error;
+
+        enc = ost->enc_ctx;
     }
 
     if (ost->source_index >= 0)
diff --git a/fftools/ffmpeg_opt.c b/fftools/ffmpeg_opt.c
index 9d1489c..334c6ec 100644
--- a/fftools/ffmpeg_opt.c
+++ b/fftools/ffmpeg_opt.c
@@ -1562,7 +1562,7 @@ static OutputStream *new_output_stream(OptionsContext *o, AVFormatContext *oc, e
     MATCH_PER_STREAM_OPT(max_muxing_queue_size, i, ost->max_muxing_queue_size, oc, st);
     ost->max_muxing_queue_size *= sizeof(AVPacket);
 
-    if (oc->oformat->flags & AVFMT_GLOBALHEADER)
+    if (oc->oformat->flags & AVFMT_GLOBALHEADER && ost->autoscale)
         ost->enc_ctx->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
 
     av_dict_copy(&ost->sws_dict, o->g->sws_dict, 0);
-- 
2.7.4