ffmpeg_opt: select a decoder after getting values for per-stream hwdec options

After applying this patch, the desired HW acceleration method is known
before selecting decoder, so we may take HW acceleration method into
account when selecting decoder for input stream in the next commit

There should be no functional changes in this patch

Signed-off-by: Haihao Xiang <haihao.xiang@intel.com>
Signed-off-by: Anton Khirnov <anton@khirnov.net>

fftools/ffmpeg_opt.c

@@ -935,72 +935,7 @@ static void add_input_streams(OptionsContext *o, AVFormatContext *ic)
             st->codecpar->codec_tag = tag;
         }
 
-        ist->dec = choose_decoder(o, ic, st);
-        ist->decoder_opts = filter_codec_opts(o->g->codec_opts, ist->st->codecpar->codec_id, ic, st, ist->dec);
-
-        ist->reinit_filters = -1;
-        MATCH_PER_STREAM_OPT(reinit_filters, i, ist->reinit_filters, ic, st);
-
-        MATCH_PER_STREAM_OPT(discard, str, discard_str, ic, st);
-        ist->user_set_discard = AVDISCARD_NONE;
-
-        if ((o->video_disable && ist->st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) ||
-            (o->audio_disable && ist->st->codecpar->codec_type == AVMEDIA_TYPE_AUDIO) ||
-            (o->subtitle_disable && ist->st->codecpar->codec_type == AVMEDIA_TYPE_SUBTITLE) ||
-            (o->data_disable && ist->st->codecpar->codec_type == AVMEDIA_TYPE_DATA))
-                ist->user_set_discard = AVDISCARD_ALL;
-
-        if (discard_str && av_opt_eval_int(&cc, discard_opt, discard_str, &ist->user_set_discard) < 0) {
-            av_log(NULL, AV_LOG_ERROR, "Error parsing discard %s.\n",
-                    discard_str);
-            exit_program(1);
-        }
-
-        ist->filter_in_rescale_delta_last = AV_NOPTS_VALUE;
-        ist->prev_pkt_pts = AV_NOPTS_VALUE;
-
-        ist->dec_ctx = avcodec_alloc_context3(ist->dec);
-        if (!ist->dec_ctx) {
-            av_log(NULL, AV_LOG_ERROR, "Error allocating the decoder context.\n");
-            exit_program(1);
-        }
-
-        ret = avcodec_parameters_to_context(ist->dec_ctx, par);
-        if (ret < 0) {
-            av_log(NULL, AV_LOG_ERROR, "Error initializing the decoder context.\n");
-            exit_program(1);
-        }
-
-        ist->decoded_frame = av_frame_alloc();
-        if (!ist->decoded_frame)
-            exit_program(1);
-
-        ist->pkt = av_packet_alloc();
-        if (!ist->pkt)
-            exit_program(1);
-
-        if (o->bitexact)
-            ist->dec_ctx->flags |= AV_CODEC_FLAG_BITEXACT;
-
-        switch (par->codec_type) {
-        case AVMEDIA_TYPE_VIDEO:
-            if(!ist->dec)
-                ist->dec = avcodec_find_decoder(par->codec_id);
-
-            // avformat_find_stream_info() doesn't set this for us anymore.
-            ist->dec_ctx->framerate = st->avg_frame_rate;
-
-            MATCH_PER_STREAM_OPT(frame_rates, str, framerate, ic, st);
-            if (framerate && av_parse_video_rate(&ist->framerate,
-                                                 framerate) < 0) {
-                av_log(NULL, AV_LOG_ERROR, "Error parsing framerate %s.\n",
-                       framerate);
-                exit_program(1);
-            }
-
-            ist->top_field_first = -1;
-            MATCH_PER_STREAM_OPT(top_field_first, i, ist->top_field_first, ic, st);
-
+        if (st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
             MATCH_PER_STREAM_OPT(hwaccels, str, hwaccel, ic, st);
             MATCH_PER_STREAM_OPT(hwaccel_output_formats, str,
                                  hwaccel_output_format, ic, st);
@@ -1066,6 +1001,73 @@ static void add_input_streams(OptionsContext *o, AVFormatContext *ic)
             }
 
             ist->hwaccel_pix_fmt = AV_PIX_FMT_NONE;
+        }
+
+        ist->dec = choose_decoder(o, ic, st);
+        ist->decoder_opts = filter_codec_opts(o->g->codec_opts, ist->st->codecpar->codec_id, ic, st, ist->dec);
+
+        ist->reinit_filters = -1;
+        MATCH_PER_STREAM_OPT(reinit_filters, i, ist->reinit_filters, ic, st);
+
+        MATCH_PER_STREAM_OPT(discard, str, discard_str, ic, st);
+        ist->user_set_discard = AVDISCARD_NONE;
+
+        if ((o->video_disable && ist->st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) ||
+            (o->audio_disable && ist->st->codecpar->codec_type == AVMEDIA_TYPE_AUDIO) ||
+            (o->subtitle_disable && ist->st->codecpar->codec_type == AVMEDIA_TYPE_SUBTITLE) ||
+            (o->data_disable && ist->st->codecpar->codec_type == AVMEDIA_TYPE_DATA))
+                ist->user_set_discard = AVDISCARD_ALL;
+
+        if (discard_str && av_opt_eval_int(&cc, discard_opt, discard_str, &ist->user_set_discard) < 0) {
+            av_log(NULL, AV_LOG_ERROR, "Error parsing discard %s.\n",
+                    discard_str);
+            exit_program(1);
+        }
+
+        ist->filter_in_rescale_delta_last = AV_NOPTS_VALUE;
+        ist->prev_pkt_pts = AV_NOPTS_VALUE;
+
+        ist->dec_ctx = avcodec_alloc_context3(ist->dec);
+        if (!ist->dec_ctx) {
+            av_log(NULL, AV_LOG_ERROR, "Error allocating the decoder context.\n");
+            exit_program(1);
+        }
+
+        ret = avcodec_parameters_to_context(ist->dec_ctx, par);
+        if (ret < 0) {
+            av_log(NULL, AV_LOG_ERROR, "Error initializing the decoder context.\n");
+            exit_program(1);
+        }
+
+        ist->decoded_frame = av_frame_alloc();
+        if (!ist->decoded_frame)
+            exit_program(1);
+
+        ist->pkt = av_packet_alloc();
+        if (!ist->pkt)
+            exit_program(1);
+
+        if (o->bitexact)
+            ist->dec_ctx->flags |= AV_CODEC_FLAG_BITEXACT;
+
+        switch (par->codec_type) {
+        case AVMEDIA_TYPE_VIDEO:
+            if(!ist->dec)
+                ist->dec = avcodec_find_decoder(par->codec_id);
+
+            // avformat_find_stream_info() doesn't set this for us anymore.
+            ist->dec_ctx->framerate = st->avg_frame_rate;
+
+            MATCH_PER_STREAM_OPT(frame_rates, str, framerate, ic, st);
+            if (framerate && av_parse_video_rate(&ist->framerate,
+                                                 framerate) < 0) {
+                av_log(NULL, AV_LOG_ERROR, "Error parsing framerate %s.\n",
+                       framerate);
+                exit_program(1);
+            }
+
+            ist->top_field_first = -1;
+            MATCH_PER_STREAM_OPT(top_field_first, i, ist->top_field_first, ic, st);
 
             break;
         case AVMEDIA_TYPE_AUDIO: