On 26/12/2019 00:55, lance.lmw...@gmail.com wrote:
> From: Limin Wang <lance.lmw...@gmail.com>
>
> FLV, MP4... will enable global_header default and place SPSs headers in
> extradata
> instead of every keyframe. So it'll failed to insert user data unregisted
> for no SPSs NAL after first AU without the patch.
>
> Please test it with below command:
> ./ffmpeg -f lavfi -i testsrc -c:v libx264 -g 25 \
> -bsf:v
> h264_metadata=sei_user_data=086f3693-b7b3-4f2c-9653-21492feee5b8+hello \
> -frames:v 150 test.mp4
>
> After applied the patch, you'll get the user data for every keyframe with
> below command:
> ./ffmpeg -i test.mp4 -vf showinfo -frames:v 150 -f null -
>
> Signed-off-by: Limin Wang <lance.lmw...@gmail.com>
> ---
> libavcodec/h264_metadata_bsf.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/libavcodec/h264_metadata_bsf.c b/libavcodec/h264_metadata_bsf.c
> index 5de74be9d6..9690ca433b 100644
> --- a/libavcodec/h264_metadata_bsf.c
> +++ b/libavcodec/h264_metadata_bsf.c
> @@ -279,7 +279,7 @@ static int h264_metadata_filter(AVBSFContext *bsf,
> AVPacket *pkt)
> {
> H264MetadataContext *ctx = bsf->priv_data;
> CodedBitstreamFragment *au = &ctx->access_unit;
> - int err, i, j, has_sps;
> + int err, i, j, has_sps, is_keyframe = 0;
> H264RawAUD aud;
>
> err = ff_bsf_get_packet_ref(bsf, pkt);
> @@ -359,11 +359,13 @@ static int h264_metadata_filter(AVBSFContext *bsf,
> AVPacket *pkt)
> goto fail;
> has_sps = 1;
> }
> + if (au->units[i].type == H264_NAL_IDR_SLICE)
> + is_keyframe = 1;
> }
>
> // Only insert the SEI in access units containing SPSs, and also
> // unconditionally in the first access unit we ever see.
> - if (ctx->sei_user_data && (has_sps || !ctx->done_first_au)) {
> + if (ctx->sei_user_data && (has_sps || !ctx->done_first_au ||
> is_keyframe)) {
> H264RawSEIPayload payload = {
> .payload_type = H264_SEI_TYPE_USER_DATA_UNREGISTERED,
> };
>
This was avoided originally because identifying key frames (or really, seek
points) in an H.264 stream is really hard. I don't particularly like the idea
of having it work in some streams but not others, depending on exactly how the
stream was encoded - hence the original decision to only include it in access
units which were already distinguished as flat-file seek-points by having the
parameter sets in them.
I guess I'm not against this in itself, but please add more of a comment in the
code explaining the rationale and noting the cases which are not included.
(And if you can cover more cases, such as recovery points, then that would be
even better.)
Thanks,
- Mark
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