On Wed, Sep 12, 2018 at 11:50 AM Michael Niedermayer
<mich...@niedermayer.cc> wrote:
>
> On Tue, Sep 11, 2018 at 03:50:57PM -0700, Jacob Trimble wrote:
> > [...]
> >
> > So how about, when we see an encrypted frame, we flush the parser
> > before skipping the frame? Can we just flush the parser and then
> > reuse it later? Or would we need to create a new parser if we saw
> > clear frames later?
>
> try/test it and review the code. only way to know for sure what works
>
> thanks
>
> [...]
> --
> Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
>
> The bravest are surely those who have the clearest vision
> of what is before them, glory and danger alike, and yet
> notwithstanding go out to meet it. -- Thucydides
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Here is a new patch that flushes the parser before returning the
encrypted packets. It also logs when it does this.
From 3955dad8070c28b021afc3304939500a09c86fcd Mon Sep 17 00:00:00 2001
From: Jacob Trimble <modma...@google.com>
Date: Tue, 28 Aug 2018 10:40:29 -0700
Subject: [PATCH] avformat/utils: Don't parse encrypted packets.
If a packet is full-sample encrypted, then packet data can't be parsed
without decrypting it. So this skips the packet parsing for those
packets. If the packet has sub-sample encryption, it is assumed that
the headers are in the clear and the parser will only need that info.
Signed-off-by: Jacob Trimble <modma...@google.com>
---
libavformat/utils.c | 41 ++++++++++++++++++++++++++++++++++++++++-
1 file changed, 40 insertions(+), 1 deletion(-)
diff --git a/libavformat/utils.c b/libavformat/utils.c
index a72f0a482e..8d84674797 100644
--- a/libavformat/utils.c
+++ b/libavformat/utils.c
@@ -27,6 +27,7 @@
#include "libavutil/avassert.h"
#include "libavutil/avstring.h"
#include "libavutil/dict.h"
+#include "libavutil/encryption_info.h"
#include "libavutil/internal.h"
#include "libavutil/mathematics.h"
#include "libavutil/opt.h"
@@ -1576,6 +1577,9 @@ static int read_frame_internal(AVFormatContext *s, AVPacket *pkt)
while (!got_packet && !s->internal->parse_queue) {
AVStream *st;
AVPacket cur_pkt;
+ uint8_t *enc_side_data;
+ int enc_side_data_size;
+ int is_full_encrypted = 0;
/* read next packet */
ret = ff_read_packet(s, &cur_pkt);
@@ -1643,7 +1647,23 @@ FF_ENABLE_DEPRECATION_WARNINGS
av_ts2str(cur_pkt.dts),
cur_pkt.size, cur_pkt.duration, cur_pkt.flags);
- if (st->need_parsing && !st->parser && !(s->flags & AVFMT_FLAG_NOPARSE)) {
+ /* if the packet is full-sample encrypted, we can't parse it. If the
+ * packet uses sub-sample encryption, assume the headers are clear and
+ * can still be parsed.
+ */
+ enc_side_data = av_packet_get_side_data(
+ &cur_pkt, AV_PKT_DATA_ENCRYPTION_INFO, &enc_side_data_size);
+ if (enc_side_data) {
+ AVEncryptionInfo *enc_info =
+ av_encryption_info_get_side_data(enc_side_data, enc_side_data_size);
+ if (enc_info) {
+ is_full_encrypted = enc_info->subsample_count == 0;
+ av_encryption_info_free(enc_info);
+ }
+ }
+
+ if (st->need_parsing && !st->parser && !(s->flags & AVFMT_FLAG_NOPARSE) &&
+ !is_full_encrypted) {
st->parser = av_parser_init(st->codecpar->codec_id);
if (!st->parser) {
av_log(s, AV_LOG_VERBOSE, "parser not found for codec "
@@ -1659,6 +1679,25 @@ FF_ENABLE_DEPRECATION_WARNINGS
st->parser->flags |= PARSER_FLAG_USE_CODEC_TS;
}
+ if (st->parser && is_full_encrypted) {
+ av_log(s, AV_LOG_VERBOSE, "skipping parsing of encrypted packets.\n");
+
+ /* flush any packets from the parser. */
+ parse_packet(s, NULL, cur_pkt.stream_index);
+ if (s->internal->parse_queue) {
+ /* if we have other packets, append this packet to the end and read
+ * from the queue instead. */
+ compute_pkt_fields(s, st, NULL, &cur_pkt, AV_NOPTS_VALUE, AV_NOPTS_VALUE);
+ ret = ff_packet_list_put(&s->internal->parse_queue,
+ &s->internal->parse_queue_end,
+ &cur_pkt, 0);
+ if (ret < 0)
+ return ret;
+ break;
+ }
+ av_assert2(!st->parser);
+ }
+
if (!st->need_parsing || !st->parser) {
/* no parsing needed: we just output the packet as is */
*pkt = cur_pkt;
--
2.19.0.397.gdd90340f6a-goog
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