[FFmpeg-devel] [PATCH 2/4] fftools/ffmpeg: stop using av_stream_get_parser()

[Anton Khirnov]

The parser is internal to the demuxer, so its state at any particular
point is not well-defined for the caller. Additionally, it is being
accessed from the main thread, while demuxing runs in a separate thread.

Use a separate parser owned by ffmpeg.c to retrieve the same
information.

Fixes races, e.g. in:
- fate-h264-brokensps-2580
- fate-h264-extradata-reload
- fate-iv8-demux
- fate-m4v-cfr
- fate-m4v
---
 fftools/ffmpeg.c     | 33 +++++++++++++++++++++++++++++++--
 fftools/ffmpeg.h     |  9 +++++++++
 fftools/ffmpeg_opt.c |  9 +++++++++
 3 files changed, 49 insertions(+), 2 deletions(-)

diff --git a/fftools/ffmpeg.c b/fftools/ffmpeg.c
index ef7177fc33..580df0443a 100644
--- a/fftools/ffmpeg.c
+++ b/fftools/ffmpeg.c
@@ -610,6 +610,9 @@ static void ffmpeg_cleanup(int ret)
         avcodec_free_context(&ist->dec_ctx);
         avcodec_parameters_free(&ist->par);
 
+        avcodec_free_context(&ist->parser_dec);
+        av_parser_close(ist->parser);
+
         av_freep(&input_streams[i]);
     }
 
@@ -2421,6 +2424,15 @@ static int process_input_packet(InputStream *ist, const AVPacket *pkt, int no_eo
         ret = av_packet_ref(avpkt, pkt);
         if (ret < 0)
             return ret;
+
+        if (ist->parser) {
+            // we do not use the parsed output, only the
+            // filled codec context fields
+            uint8_t *dummy;
+            int      dummy_size;
+            av_parser_parse2(ist->parser, ist->parser_dec, &dummy, &dummy_size,
+                             pkt->data, pkt->size, pkt->pts, pkt->dts, pkt->pos);
+        }
     }
 
     if (pkt && pkt->dts != AV_NOPTS_VALUE) {
@@ -2452,7 +2464,8 @@ static int process_input_packet(InputStream *ist, const AVPacket *pkt, int no_eo
                 if (pkt && pkt->duration) {
                     duration_dts = av_rescale_q(pkt->duration, ist->st->time_base, AV_TIME_BASE_Q);
                 } else if(ist->dec_ctx->framerate.num != 0 && ist->dec_ctx->framerate.den != 0) {
-                    int ticks= av_stream_get_parser(ist->st) ? av_stream_get_parser(ist->st)->repeat_pict+1 : ist->dec_ctx->ticks_per_frame;
+                    int ticks = ist->parser ? ist->parser->repeat_pict + 1 :
+                                              ist->dec_ctx->ticks_per_frame;
                     duration_dts = ((int64_t)AV_TIME_BASE *
                                     ist->dec_ctx->framerate.den * ticks) /
                                     ist->dec_ctx->framerate.num / ist->dec_ctx->ticks_per_frame;
@@ -2555,7 +2568,8 @@ static int process_input_packet(InputStream *ist, const AVPacket *pkt, int no_eo
             } else if (pkt->duration) {
                 ist->next_dts += av_rescale_q(pkt->duration, ist->st->time_base, AV_TIME_BASE_Q);
             } else if(ist->dec_ctx->framerate.num != 0) {
-                int ticks= av_stream_get_parser(ist->st) ? av_stream_get_parser(ist->st)->repeat_pict + 1 : ist->dec_ctx->ticks_per_frame;
+                int ticks = ist->parser ? ist->parser->repeat_pict + 1 :
+                                          ist->dec_ctx->ticks_per_frame;
                 ist->next_dts += ((int64_t)AV_TIME_BASE *
                                   ist->dec_ctx->framerate.den * ticks) /
                                   ist->dec_ctx->framerate.num / ist->dec_ctx->ticks_per_frame;
@@ -2688,6 +2702,21 @@ static int init_input_stream(int ist_index, char *error, int error_len)
         assert_avoptions(ist->decoder_opts);
     }
 
+    if (ist->parser) {
+        AVCodecParameters *par_tmp;
+
+        par_tmp = avcodec_parameters_alloc();
+        if (!par_tmp)
+            return AVERROR(ENOMEM);
+
+        ret = avcodec_parameters_from_context(par_tmp, ist->dec_ctx);
+        if (ret >= 0)
+            ret = avcodec_parameters_to_context(ist->parser_dec, par_tmp);
+        avcodec_parameters_free(&par_tmp);
+        if (ret < 0)
+            return ret;
+    }
+
     ist->next_pts = AV_NOPTS_VALUE;
     ist->next_dts = AV_NOPTS_VALUE;
 
diff --git a/fftools/ffmpeg.h b/fftools/ffmpeg.h
index 44cc23fa84..f67a2f1d1d 100644
--- a/fftools/ffmpeg.h
+++ b/fftools/ffmpeg.h
@@ -334,6 +334,15 @@ typedef struct InputStream {
     AVFrame *decoded_frame;
     AVPacket *pkt;
 
+    /**
+     * Parser for timestamp processing.
+     */
+    AVCodecParserContext *parser;
+    /**
+     * Codec context needed by parsing.
+     */
+    AVCodecContext       *parser_dec;
+
     int64_t       prev_pkt_pts;
     int64_t       start;     /* time when read started */
     /* predicted dts of the next packet read for this stream or (when there are
diff --git a/fftools/ffmpeg_opt.c b/fftools/ffmpeg_opt.c
index 30ca5cd609..a505c7b26f 100644
--- a/fftools/ffmpeg_opt.c
+++ b/fftools/ffmpeg_opt.c
@@ -1065,6 +1065,15 @@ static void add_input_streams(OptionsContext *o, AVFormatContext *ic)
             ist->top_field_first = -1;
             MATCH_PER_STREAM_OPT(top_field_first, i, ist->top_field_first, ic, st);
 
+            ist->parser = av_parser_init(ist->dec->id);
+            if (ist->parser) {
+                ist->parser->flags |= PARSER_FLAG_COMPLETE_FRAMES;
+
+                ist->parser_dec = avcodec_alloc_context3(NULL);
+                if (!ist->parser_dec)
+                    exit_program(1);
+            }
+
             break;
         case AVMEDIA_TYPE_AUDIO:
             ist->guess_layout_max = INT_MAX;
-- 
2.35.1