fftools/ffmpeg: rework -enc_time_base handling

Read the timebase from FrameData rather than the input stream. This
should fix #10393 and generally be more reliable.

Replace the use of '-1' to indicate demuxing timebase with the string
'demux'. Also allow to request filter timebase with
'-enc_time_base filter'.

doc/ffmpeg.texi

@@ -1812,10 +1812,11 @@ Assign a default value according to the media type.
 
 For video - use 1/framerate, for audio - use 1/samplerate.
 
-@item -1
-Use the input stream timebase when possible.
+@item demux
+Use the timebase from the demuxer.
 
-If an input stream is not available, the default timebase will be used.
+@item filter
+Use the timebase from the filtergraph.
 
 @item >0
 Use the provided number as the timebase.

fftools/ffmpeg.h

@@ -56,6 +56,7 @@
 #define FFMPEG_ROTATION_METADATA 1
 #define FFMPEG_OPT_QPHIST 1
 #define FFMPEG_OPT_ADRIFT_THRESHOLD 1
+#define FFMPEG_OPT_ENC_TIME_BASE_NUM 1
 
 enum VideoSyncMethod {
     VSYNC_AUTO = -1,
@@ -66,6 +67,11 @@ enum VideoSyncMethod {
     VSYNC_DROP,
 };
 
+enum EncTimeBase {
+    ENC_TIME_BASE_DEMUX  = -1,
+    ENC_TIME_BASE_FILTER = -2,
+};
+
 #define MAX_STREAMS 1024    /* arbitrary sanity check value */
 
 enum HWAccelID {

fftools/ffmpeg_enc.c

@@ -264,8 +264,20 @@ int enc_open(OutputStream *ost, AVFrame *frame)
                       fr.num, fr.den, 65535);
         }
 
-        enc_ctx->time_base = ost->enc_timebase.num > 0 ? ost->enc_timebase :
-                             av_inv_q(fr);
+        if (ost->enc_timebase.num == ENC_TIME_BASE_DEMUX) {
+            if (fd->dec.tb.num <= 0 || fd->dec.tb.den <= 0) {
+                av_log(ost, AV_LOG_ERROR,
+                       "Demuxing timebase not available - cannot use it for encoding\n");
+                return AVERROR(EINVAL);
+            }
+
+            enc_ctx->time_base = fd->dec.tb;
+        } else if (ost->enc_timebase.num == ENC_TIME_BASE_FILTER) {
+            enc_ctx->time_base = frame->time_base;
+        } else {
+            enc_ctx->time_base = ost->enc_timebase.num > 0 ? ost->enc_timebase :
+                                 av_inv_q(fr);
+        }
 
         if (!(enc_ctx->time_base.num && enc_ctx->time_base.den))
             enc_ctx->time_base = frame->time_base;

fftools/ffmpeg_mux_init.c

@@ -1171,20 +1171,27 @@ static int ost_add(Muxer *mux, const OptionsContext *o, enum AVMediaType type,
         MATCH_PER_STREAM_OPT(enc_time_bases, str, enc_time_base, oc, st);
         if (enc_time_base) {
             AVRational q;
-            if (av_parse_ratio(&q, enc_time_base, INT_MAX, 0, NULL) < 0 ||
-                q.den <= 0) {
-                av_log(ost, AV_LOG_FATAL, "Invalid time base: %s\n", enc_time_base);
-                return AVERROR(EINVAL);
-            }
-            if (q.num < 0) {
-                if (!ost->ist) {
-                    av_log(ost, AV_LOG_FATAL,
-                           "Cannot use input stream timebase for encoding - "
-                           "no input stream available\n");
-                    return AVERROR(EINVAL);
+            if (!strcmp(enc_time_base, "demux")) {
+                q = (AVRational){ ENC_TIME_BASE_DEMUX, 0 };
+            } else if (!strcmp(enc_time_base, "filter")) {
+                q = (AVRational){ ENC_TIME_BASE_FILTER, 0 };
+            } else {
+                ret = av_parse_ratio(&q, enc_time_base, INT_MAX, 0, NULL);
+                if (ret < 0 || q.den <= 0
+#if !FFMPEG_OPT_ENC_TIME_BASE_NUM
+                    || q.num < 0
+#endif
+                    ) {
+                    av_log(ost, AV_LOG_FATAL, "Invalid time base: %s\n", enc_time_base);
+                    return ret < 0 ? ret : AVERROR(EINVAL);
                 }
-                q = ost->ist->st->time_base;
+#if FFMPEG_OPT_ENC_TIME_BASE_NUM
+                if (q.num < 0)
+                    av_log(ost, AV_LOG_WARNING, "-enc_time_base -1 is deprecated,"
+                           " use -enc_timebase demux\n");
+#endif
             }
+
             ost->enc_timebase = q;
         }
     } else {

tests/fate/video.mak

@@ -270,7 +270,7 @@ FATE_VIDEO-$(call FRAMECRC, MXG, MXPEG) += fate-mxpeg
 fate-mxpeg: CMD = framecrc -idct simple -flags +bitexact -i $(TARGET_SAMPLES)/mxpeg/m1.mxg -an
 
 FATE_NUV += fate-nuv-rtjpeg
-fate-nuv-rtjpeg: CMD = framecrc -idct simple -i $(TARGET_SAMPLES)/nuv/Today.nuv -an -enc_time_base -1
+fate-nuv-rtjpeg: CMD = framecrc -idct simple -i $(TARGET_SAMPLES)/nuv/Today.nuv -an -enc_time_base demux
 
 FATE_NUV += fate-nuv-rtjpeg-fh
 fate-nuv-rtjpeg-fh: CMD = framecrc -idct simple -i $(TARGET_SAMPLES)/nuv/rtjpeg_frameheader.nuv -an