fftools/ffmpeg_demux: implement -bsf for input

Previously bitstream filters could only be applied right before muxing,
this allows to apply them right after demuxing.

Changelog

@@ -19,6 +19,7 @@ version <next>:
 - VVC decoder
 - fsync filter
 - Raw Captions with Time (RCWT) closed caption muxer
+- ffmpeg CLI -bsf option may now be used for input as well as output
 
 version 6.1:
 - libaribcaption decoder

doc/ffmpeg.texi

@@ -2093,13 +2093,13 @@ an output mpegts file:
 ffmpeg -i inurl -streamid 0:33 -streamid 1:36 out.ts
 @end example
 
-@item -bsf[:@var{stream_specifier}] @var{bitstream_filters} (@emph{output,per-stream})
-Apply bitstream filters to matching streams.
+@item -bsf[:@var{stream_specifier}] @var{bitstream_filters} (@emph{input/output,per-stream})
+Apply bitstream filters to matching streams. The filters are applied to each
+packet as it is received from the demuxer (when used as an input option) or
+before it is sent to the muxer (when used as an output option).
 
 @var{bitstream_filters} is a comma-separated list of bitstream filter
-specifications. The specified bitstream filters are applied to coded packets in
-the order they are written in. Each bitstream filter specification is of the
-form
+specifications, each of the form
 @example
 @var{filter}[=@var{optname0}=@var{optval0}:@var{optname1}=@var{optval1}:...]
 @end example
@@ -2107,12 +2107,22 @@ Any of the ',=:' characters that are to be a part of an option value need to be
 escaped with a backslash.
 
 Use the @code{-bsfs} option to get the list of bitstream filters.
+
+E.g.
 @example
-ffmpeg -i h264.mp4 -c:v copy -bsf:v h264_mp4toannexb -an out.h264
+ffmpeg -bsf:v h264_mp4toannexb -i h264.mp4 -c:v copy -an out.h264
 @end example
+applies the @code{h264_mp4toannexb} bitstream filter (which converts
+MP4-encapsulated H.264 stream to Annex B) to the @emph{input} video stream.
+
+On the other hand,
 @example
 ffmpeg -i file.mov -an -vn -bsf:s mov2textsub -c:s copy -f rawvideo sub.txt
 @end example
+applies the @code{mov2textsub} bitstream filter (which extracts text from MOV
+subtitles) to the @emph{output} subtitle stream. Note, however, that since both
+examples use @code{-c copy}, it matters little whether the filters are applied
+on input or output - that would change if transcoding was happening.
 
 @item -tag[:@var{stream_specifier}] @var{codec_tag} (@emph{input/output,per-stream})
 Force a tag/fourcc for matching streams.

fftools/ffmpeg_demux.c

@@ -34,6 +34,7 @@
 #include "libavutil/time.h"
 #include "libavutil/timestamp.h"
 
+#include "libavcodec/bsf.h"
 #include "libavcodec/packet.h"
 
 #include "libavformat/avformat.h"
@@ -71,6 +72,8 @@ typedef struct DemuxStream {
 
     const AVCodecDescriptor *codec_desc;
 
+    AVBSFContext *bsf;
+
     /* number of packets successfully read for this stream */
     uint64_t nb_packets;
     // combined size of all the packets read
@@ -118,6 +121,8 @@ typedef struct Demuxer {
 typedef struct DemuxThreadContext {
     // packet used for reading from the demuxer
     AVPacket *pkt_demux;
+    // packet for reading from BSFs
+    AVPacket *pkt_bsf;
 } DemuxThreadContext;
 
 static DemuxStream *ds_from_ist(InputStream *ist)
@@ -513,13 +518,17 @@ static int do_send(Demuxer *d, DemuxStream *ds, AVPacket *pkt, unsigned flags,
     return 0;
 }
 
-static int demux_send(Demuxer *d, DemuxStream *ds, AVPacket *pkt, unsigned flags)
+static int demux_send(Demuxer *d, DemuxThreadContext *dt, DemuxStream *ds,
+                      AVPacket *pkt, unsigned flags)
 {
     InputFile  *f = &d->f;
     int ret;
 
+    // pkt can be NULL only when flushing BSFs
+    av_assert0(ds->bsf || pkt);
+
     // send heartbeat for sub2video streams
-    if (d->pkt_heartbeat && pkt->pts != AV_NOPTS_VALUE) {
+    if (d->pkt_heartbeat && pkt && pkt->pts != AV_NOPTS_VALUE) {
         for (int i = 0; i < f->nb_streams; i++) {
             DemuxStream *ds1 = ds_from_ist(f->streams[i]);
 
@@ -537,10 +546,69 @@ static int demux_send(Demuxer *d, DemuxStream *ds, AVPacket *pkt, unsigned flags
         }
     }
 
+    if (ds->bsf) {
+        if (pkt)
+            av_packet_rescale_ts(pkt, pkt->time_base, ds->bsf->time_base_in);
+
+        ret = av_bsf_send_packet(ds->bsf, pkt);
+        if (ret < 0) {
+            if (pkt)
+                av_packet_unref(pkt);
+            av_log(ds, AV_LOG_ERROR, "Error submitting a packet for filtering: %s\n",
+                   av_err2str(ret));
+            return ret;
+        }
+
+        while (1) {
+            ret = av_bsf_receive_packet(ds->bsf, dt->pkt_bsf);
+            if (ret == AVERROR(EAGAIN))
+                return 0;
+            else if (ret < 0) {
+                if (ret != AVERROR_EOF)
+                    av_log(ds, AV_LOG_ERROR,
+                           "Error applying bitstream filters to a packet: %s\n",
+                           av_err2str(ret));
+                return ret;
+            }
+
+            dt->pkt_bsf->time_base = ds->bsf->time_base_out;
+
+            ret = do_send(d, ds, dt->pkt_bsf, 0, "filtered");
+            if (ret < 0) {
+                av_packet_unref(dt->pkt_bsf);
+                return ret;
+            }
+        }
+    } else {
         ret = do_send(d, ds, pkt, flags, "demuxed");
         if (ret < 0)
             return ret;
+    }
 
+    return 0;
+}
+
+static int demux_bsf_flush(Demuxer *d, DemuxThreadContext *dt)
+{
+    InputFile *f = &d->f;
+    int ret;
+
+    for (unsigned i = 0; i < f->nb_streams; i++) {
+        DemuxStream *ds = ds_from_ist(f->streams[i]);
+
+        if (!ds->bsf)
+            continue;
+
+        ret = demux_send(d, dt, ds, NULL, 0);
+        ret = (ret == AVERROR_EOF) ? 0 : (ret < 0) ? ret : AVERROR_BUG;
+        if (ret < 0) {
+            av_log(ds, AV_LOG_ERROR, "Error flushing BSFs: %s\n",
+                   av_err2str(ret));
+            return ret;
+        }
+
+        av_bsf_flush(ds->bsf);
+    }
 
     return 0;
 }
@@ -573,6 +641,7 @@ static void thread_set_name(InputFile *f)
 static void demux_thread_uninit(DemuxThreadContext *dt)
 {
     av_packet_free(&dt->pkt_demux);
+    av_packet_free(&dt->pkt_bsf);
 
     memset(dt, 0, sizeof(*dt));
 }
@@ -585,6 +654,10 @@ static int demux_thread_init(DemuxThreadContext *dt)
     if (!dt->pkt_demux)
         return AVERROR(ENOMEM);
 
+    dt->pkt_bsf = av_packet_alloc();
+    if (!dt->pkt_bsf)
+        return AVERROR(ENOMEM);
+
     return 0;
 }
 
@@ -619,10 +692,22 @@ static void *input_thread(void *arg)
             continue;
         }
         if (ret < 0) {
+            int ret_bsf;
+
+            if (ret == AVERROR_EOF)
+                av_log(d, AV_LOG_VERBOSE, "EOF while reading input\n");
+            else {
+                av_log(d, AV_LOG_ERROR, "Error during demuxing: %s\n",
+                       av_err2str(ret));
+                ret = exit_on_error ? ret : 0;
+            }
+
+            ret_bsf = demux_bsf_flush(d, &dt);
+            ret = err_merge(ret == AVERROR_EOF ? 0 : ret, ret_bsf);
+
             if (d->loop) {
                 /* signal looping to our consumers */
                 dt.pkt_demux->stream_index = -1;
-
                 ret = sch_demux_send(d->sch, f->index, dt.pkt_demux, 0);
                 if (ret >= 0)
                     ret = seek_to_start(d, (Timestamp){ .ts = dt.pkt_demux->pts,
@@ -633,14 +718,6 @@ static void *input_thread(void *arg)
                 /* fallthrough to the error path */
             }
 
-            if (ret == AVERROR_EOF)
-                av_log(d, AV_LOG_VERBOSE, "EOF while reading input\n");
-            else {
-                av_log(d, AV_LOG_ERROR, "Error during demuxing: %s\n",
-                       av_err2str(ret));
-                ret = exit_on_error ? ret : 0;
-            }
-
             break;
         }
 
@@ -677,7 +754,7 @@ static void *input_thread(void *arg)
         if (d->readrate)
             readrate_sleep(d);
 
-        ret = demux_send(d, ds, dt.pkt_demux, send_flags);
+        ret = demux_send(d, &dt, ds, dt.pkt_demux, send_flags);
         if (ret < 0)
             break;
     }
@@ -735,9 +812,11 @@ static void demux_final_stats(Demuxer *d)
 static void ist_free(InputStream **pist)
 {
     InputStream *ist = *pist;
+    DemuxStream *ds;
 
     if (!ist)
         return;
+    ds = ds_from_ist(ist);
 
     dec_free(&ist->decoder);
 
@@ -749,6 +828,8 @@ static void ist_free(InputStream **pist)
     avcodec_free_context(&ist->dec_ctx);
     avcodec_parameters_free(&ist->par);
 
+    av_bsf_free(&ds->bsf);
+
     av_freep(pist);
 }
 
@@ -1039,6 +1120,7 @@ static int ist_add(const OptionsContext *o, Demuxer *d, AVStream *st)
     const char *hwaccel = NULL;
     char *hwaccel_output_format = NULL;
     char *codec_tag = NULL;
+    char *bsfs = NULL;
     char *next;
     char *discard_str = NULL;
     int ret;
@@ -1258,6 +1340,33 @@ static int ist_add(const OptionsContext *o, Demuxer *d, AVStream *st)
         return ret;
     }
 
+    MATCH_PER_STREAM_OPT(bitstream_filters, str, bsfs, ic, st);
+    if (bsfs) {
+        ret = av_bsf_list_parse_str(bsfs, &ds->bsf);
+        if (ret < 0) {
+            av_log(ist, AV_LOG_ERROR,
+                   "Error parsing bitstream filter sequence '%s': %s\n",
+                   bsfs, av_err2str(ret));
+            return ret;
+        }
+
+        ret = avcodec_parameters_copy(ds->bsf->par_in, ist->par);
+        if (ret < 0)
+            return ret;
+        ds->bsf->time_base_in = ist->st->time_base;
+
+        ret = av_bsf_init(ds->bsf);
+        if (ret < 0) {
+            av_log(ist, AV_LOG_ERROR, "Error initializing bitstream filters: %s\n",
+                   av_err2str(ret));
+            return ret;
+        }
+
+        ret = avcodec_parameters_copy(ist->par, ds->bsf->par_out);
+        if (ret < 0)
+            return ret;
+    }
+
     ds->codec_desc = avcodec_descriptor_get(ist->par->codec_id);
 
     return 0;

fftools/ffmpeg_opt.c

@@ -1919,7 +1919,7 @@ const OptionDef options[] = {
         "0 = use frame rate (video) or sample rate (audio),"
         "-1 = match source time base", "ratio" },
 
-    { "bsf", OPT_TYPE_STRING, OPT_SPEC | OPT_EXPERT | OPT_OUTPUT,
+    { "bsf", OPT_TYPE_STRING, OPT_SPEC | OPT_EXPERT | OPT_OUTPUT | OPT_INPUT,
         { .off = OFFSET(bitstream_filters) },
         "A comma-separated list of bitstream filters", "bitstream_filters", },
 

tests/fate/ffmpeg.mak

@@ -256,3 +256,8 @@ FATE_SAMPLES_FFMPEG-$(call FRAMECRC, MPEGVIDEO, MPEG2VIDEO) += fate-ffmpeg-input
 fate-ffmpeg-error-rate-fail: CMD = ffmpeg -i $(TARGET_SAMPLES)/mkv/h264_tta_undecodable.mkv -c:v copy -f null -; test $$? -eq 69
 fate-ffmpeg-error-rate-pass: CMD = ffmpeg -i $(TARGET_SAMPLES)/mkv/h264_tta_undecodable.mkv -c:v copy -f null - -max_error_rate 1
 FATE_SAMPLES_FFMPEG-$(call ENCDEC, PCM_S16LE TTA, NULL MATROSKA) += fate-ffmpeg-error-rate-fail fate-ffmpeg-error-rate-pass
+
+# test input -bsf
+# use -stream_loop, because it tests flushing bsfs
+fate-ffmpeg-bsf-input: CMD = framecrc -stream_loop 2 -bsf setts=PTS*2 -i $(TARGET_SAMPLES)/hevc/extradata-reload-multi-stsd.mov -c copy
+FATE_SAMPLES_FFMPEG-$(call FRAMECRC, MOV, , SETTS_BSF) += fate-ffmpeg-bsf-input

tests/ref/fate/ffmpeg-bsf-input

@@ -0,0 +1,18 @@
+#extradata 0:      110, 0xb4031479
+#tb 0: 1/25
+#media_type 0: video
+#codec_id 0: hevc
+#dimensions 0: 128x128
+#sar 0: 1/1
+0,          0,          0,        1,     2108, 0x57c38f64
+0,          2,          2,        1,       31, 0xabe10d25, F=0x0
+0,          4,          4,        1,     1915, 0xd430347f, S=1,      109
+0,          6,          6,        1,       35, 0xc4ad0d4c, F=0x0
+0,          8,          8,        1,     2108, 0x57c38f64, S=1,      110
+0,         10,         10,        1,       31, 0xabe10d25, F=0x0
+0,         12,         12,        1,     1915, 0xd430347f, S=1,      109
+0,         14,         14,        1,       35, 0xc4ad0d4c, F=0x0
+0,         16,         16,        1,     2108, 0x57c38f64, S=1,      110
+0,         18,         18,        1,       31, 0xabe10d25, F=0x0
+0,         20,         20,        1,     1915, 0xd430347f, S=1,      109
+0,         22,         22,        1,       35, 0xc4ad0d4c, F=0x0