lavc: Add filter_units bitstream filter

This can remove units with types in or not in a given set from a stream.
For example, it can be used to remove all non-VCL NAL units from an H.264 or
H.265 stream.

configure

@@ -2919,6 +2919,7 @@ vc1_parser_select="vc1dsp"
 
 # bitstream_filters
 aac_adtstoasc_bsf_select="adts_header"
+filter_units_bsf_select="cbs"
 h264_metadata_bsf_select="cbs_h264"
 h264_redundant_pps_bsf_select="cbs_h264"
 hevc_metadata_bsf_select="cbs_h265"

doc/bitstream_filters.texi

@@ -93,6 +93,35 @@ When this option is enabled, the long-term headers are removed from the
 bitstream after extraction.
 @end table
 
+@section filter_units
+
+Remove units with types in or not in a given set from the stream.
+
+@table @option
+@item pass_types
+List of unit types or ranges of unit types to pass through while removing
+all others.  This is specified as a '|'-separated list of unit type values
+or ranges of values with '-'.
+
+@item remove_types
+Identical to @option{pass_types}, except the units in the given set
+removed and all others passed through.
+@end table
+
+Extradata is unchanged by this transformation, but note that if the stream
+contains inline parameter sets then the output may be unusable if they are
+removed.
+
+For example, to remove all non-VCL NAL units from an H.264 stream:
+@example
+ffmpeg -i INPUT -c:v copy -bsf:v 'filter_units=pass_types=1-5' OUTPUT
+@end example
+
+To remove all AUDs, SEI and filler from an H.265 stream:
+@example
+ffmpeg -i INPUT -c:v copy -bsf:v 'filter_units=remove_types=35|38-40' OUTPUT
+@end example
+
 @section hapqa_extract
 
 Extract Rgb or Alpha part of an HAPQA file, without recompression, in order to create an HAPQ or an HAPAlphaOnly file.

libavcodec/Makefile

@@ -1043,6 +1043,7 @@ OBJS-$(CONFIG_DUMP_EXTRADATA_BSF)         += dump_extradata_bsf.o
 OBJS-$(CONFIG_DCA_CORE_BSF)               += dca_core_bsf.o
 OBJS-$(CONFIG_EXTRACT_EXTRADATA_BSF)      += extract_extradata_bsf.o    \
                                              h2645_parse.o
+OBJS-$(CONFIG_FILTER_UNITS_BSF)           += filter_units_bsf.o
 OBJS-$(CONFIG_H264_METADATA_BSF)          += h264_metadata_bsf.o
 OBJS-$(CONFIG_H264_MP4TOANNEXB_BSF)       += h264_mp4toannexb_bsf.o
 OBJS-$(CONFIG_H264_REDUNDANT_PPS_BSF)     += h264_redundant_pps_bsf.o

libavcodec/bitstream_filters.c

@@ -29,6 +29,7 @@ extern const AVBitStreamFilter ff_chomp_bsf;
 extern const AVBitStreamFilter ff_dump_extradata_bsf;
 extern const AVBitStreamFilter ff_dca_core_bsf;
 extern const AVBitStreamFilter ff_extract_extradata_bsf;
+extern const AVBitStreamFilter ff_filter_units_bsf;
 extern const AVBitStreamFilter ff_h264_metadata_bsf;
 extern const AVBitStreamFilter ff_h264_mp4toannexb_bsf;
 extern const AVBitStreamFilter ff_h264_redundant_pps_bsf;

libavcodec/filter_units_bsf.c

+/*
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <stdlib.h>
+
+#include "libavutil/common.h"
+#include "libavutil/opt.h"
+
+#include "bsf.h"
+#include "cbs.h"
+
+
+typedef struct FilterUnitsContext {
+    const AVClass *class;
+
+    CodedBitstreamContext *cbc;
+    CodedBitstreamFragment fragment;
+
+    const char *pass_types;
+    const char *remove_types;
+
+    enum {
+        NOOP,
+        PASS,
+        REMOVE,
+    } mode;
+    CodedBitstreamUnitType *type_list;
+    int nb_types;
+} FilterUnitsContext;
+
+
+static int filter_units_make_type_list(const char *list_string,
+                                       CodedBitstreamUnitType **type_list,
+                                       int *nb_types)
+{
+    CodedBitstreamUnitType *list = NULL;
+    int pass, count;
+
+    for (pass = 1; pass <= 2; pass++) {
+        long value, range_start, range_end;
+        const char *str;
+        char *value_end;
+
+        count = 0;
+        for (str = list_string; *str;) {
+            value = strtol(str, &value_end, 0);
+            if (str == value_end)
+                goto invalid;
+            str = (const char *)value_end;
+            if (*str == '-') {
+                ++str;
+                range_start = value;
+                range_end   = strtol(str, &value_end, 0);
+                if (str == value_end)
+                    goto invalid;
+
+                for (value = range_start; value < range_end; value++) {
+                    if (pass == 2)
+                        list[count] = value;
+                    ++count;
+                }
+            } else {
+                if (pass == 2)
+                    list[count] = value;
+                ++count;
+            }
+            if (*str == '|')
+                ++str;
+        }
+        if (pass == 1) {
+            list = av_malloc_array(count, sizeof(*list));
+            if (!list)
+                return AVERROR(ENOMEM);
+        }
+    }
+
+    *type_list = list;
+    *nb_types  = count;
+    return 0;
+
+invalid:
+    av_freep(&list);
+    return AVERROR(EINVAL);
+}
+
+static int filter_units_filter(AVBSFContext *bsf, AVPacket *out)
+{
+    FilterUnitsContext      *ctx = bsf->priv_data;
+    CodedBitstreamFragment *frag = &ctx->fragment;
+    AVPacket *in = NULL;
+    int err, i, j;
+
+    while (1) {
+        err = ff_bsf_get_packet(bsf, &in);
+        if (err < 0)
+            return err;
+
+        if (ctx->mode == NOOP) {
+            av_packet_move_ref(out, in);
+            av_packet_free(&in);
+            return 0;
+        }
+
+        err = ff_cbs_read_packet(ctx->cbc, frag, in);
+        if (err < 0) {
+            av_log(bsf, AV_LOG_ERROR, "Failed to read packet.\n");
+            goto fail;
+        }
+
+        for (i = 0; i < frag->nb_units; i++) {
+            for (j = 0; j < ctx->nb_types; j++) {
+                if (frag->units[i].type == ctx->type_list[j])
+                    break;
+            }
+            if (ctx->mode == REMOVE ? j <  ctx->nb_types
+                                    : j >= ctx->nb_types) {
+                ff_cbs_delete_unit(ctx->cbc, frag, i);
+                --i;
+            }
+        }
+
+        if (frag->nb_units > 0)
+            break;
+
+        // Don't return packets with nothing in them.
+        av_packet_free(&in);
+        ff_cbs_fragment_uninit(ctx->cbc, frag);
+    }
+
+    err = ff_cbs_write_packet(ctx->cbc, out, frag);
+    if (err < 0) {
+        av_log(bsf, AV_LOG_ERROR, "Failed to write packet.\n");
+        goto fail;
+    }
+
+    err = av_packet_copy_props(out, in);
+    if (err < 0)
+        goto fail;
+
+fail:
+    ff_cbs_fragment_uninit(ctx->cbc, frag);
+    av_packet_free(&in);
+
+    return err;
+}
+
+static int filter_units_init(AVBSFContext *bsf)
+{
+    FilterUnitsContext *ctx = bsf->priv_data;
+    int err;
+
+    if (ctx->pass_types && ctx->remove_types) {
+        av_log(bsf, AV_LOG_ERROR, "Exactly one of pass_types or "
+               "remove_types is required.\n");
+        return AVERROR(EINVAL);
+    }
+
+    if (ctx->pass_types) {
+        ctx->mode = PASS;
+        err = filter_units_make_type_list(ctx->pass_types,
+                                          &ctx->type_list, &ctx->nb_types);
+        if (err < 0) {
+            av_log(bsf, AV_LOG_ERROR, "Failed to parse pass_types.\n");
+            return err;
+        }
+    } else if (ctx->remove_types) {
+        ctx->mode = REMOVE;
+        err = filter_units_make_type_list(ctx->remove_types,
+                                          &ctx->type_list, &ctx->nb_types);
+        if (err < 0) {
+            av_log(bsf, AV_LOG_ERROR, "Failed to parse remove_types.\n");
+            return err;
+        }
+    } else {
+        return 0;
+    }
+
+    err = ff_cbs_init(&ctx->cbc, bsf->par_in->codec_id, bsf);
+    if (err < 0)
+        return err;
+
+    // Don't actually decompose anything, we only want the unit data.
+    ctx->cbc->decompose_unit_types    = ctx->type_list;
+    ctx->cbc->nb_decompose_unit_types = 0;
+
+    if (bsf->par_in->extradata) {
+        CodedBitstreamFragment ps;
+
+        err = ff_cbs_read_extradata(ctx->cbc, &ps, bsf->par_in);
+        if (err < 0) {
+            av_log(bsf, AV_LOG_ERROR, "Failed to read extradata.\n");
+        } else {
+            err = ff_cbs_write_extradata(ctx->cbc, bsf->par_out, &ps);
+            if (err < 0)
+                av_log(bsf, AV_LOG_ERROR, "Failed to write extradata.\n");
+        }
+
+        ff_cbs_fragment_uninit(ctx->cbc, &ps);
+    }
+
+    return err;
+}
+
+static void filter_units_close(AVBSFContext *bsf)
+{
+    FilterUnitsContext *ctx = bsf->priv_data;
+
+    av_freep(&ctx->type_list);
+
+    ff_cbs_close(&ctx->cbc);
+}
+
+#define OFFSET(x) offsetof(FilterUnitsContext, x)
+#define FLAGS (AV_OPT_FLAG_VIDEO_PARAM|AV_OPT_FLAG_BSF_PARAM)
+static const AVOption filter_units_options[] = {
+    { "pass_types",   "List of unit types to pass through the filter.",
+        OFFSET(pass_types),   AV_OPT_TYPE_STRING,
+        { .str = NULL }, .flags = FLAGS },
+    { "remove_types", "List of unit types to remove in the filter.",
+        OFFSET(remove_types), AV_OPT_TYPE_STRING,
+        { .str = NULL }, .flags = FLAGS },
+
+    { NULL }
+};
+
+static const AVClass filter_units_class = {
+    .class_name = "filter_units",
+    .item_name  = av_default_item_name,
+    .option     = filter_units_options,
+    .version    = LIBAVUTIL_VERSION_INT,
+};
+
+const AVBitStreamFilter ff_filter_units_bsf = {
+    .name           = "filter_units",
+    .priv_data_size = sizeof(FilterUnitsContext),
+    .priv_class     = &filter_units_class,
+    .init           = &filter_units_init,
+    .close          = &filter_units_close,
+    .filter         = &filter_units_filter,
+    .codec_ids      = ff_cbs_all_codec_ids,
+};