id	summary	reporter	owner	description	type	status	priority	component	version	resolution	keywords	cc	blockedby	blocking	reproduced	analyzed
8465	avformat_find_stream_info does not fill MPEG2-TS/HEVC resolution with HEVC decoder disabled	Damian Dyńdo		"Summary of the bug:

I've found that if FFmpeg is built with HEVC decoder disabled (or does not have ""hevc"" decoder on whitelist in CLI), it will fail to acquire basic metadata (e.g. resolution, color characteristics, etc.) even though internal parsers are enabled and do parse NAL units like SPS or VUI from it (and during the call too).

It seems that in most cases it works because at the end of this logic if FFmpeg detects that the parameters are not set, it tries to decode the first sample which then correctly sets resolution and other stream metadata.


How to reproduce:

Either:
1. Build FFmpeg without HEVC decoder
2. Use FFmpeg API (even example code is fine) - avformat_find_stream_info() function on opened MPEG2-TS/HEVC file
3. Watch errors logged and check out that video stream in AVFormatContext does not have basic metadata like resolution, color space, etc. filled correctly.
4. If you enable logs on very high level, you will actually see that it does parse SPS NAL unit correctly.

or:
{{{
% ffprobe -v 50 -codec_whitelist h265 h1.ts
%
% ...
% [NULL @ 0x3ed7a528ca00] Could not find codec parameters for stream 0 (Video: hevc, 1 reference frame (HEVC / 0x43564548), none): unspecified size
% ...
}}}

I've used h1.ts file from #3487 (http://trac.ffmpeg.org/ticket/3487) and it reproduces just as well.

------------------

Some analysis 

I've found out that SPS NAL unit (and others) are parsed on such stack trace:

- `ff_hevc_decode_nal_sps()`
- `hevc_parse()`
- `av_parser_parse2()`
- `parse_packet()`
- `read_frame_internal()`
- `avformat_find_stream_info()`

The problem is that this information parsed there is not propagated higher (outside of the parser (AVCodecParserContext) to the codec (AVCodecContext)). This can be seen in `av_parser_parse2()` where there is code like:

{{{
%    if (avctx->codec_type == AVMEDIA_TYPE_VIDEO) {
%        FILL(field_order);
%    }
}}}

This is one place in code I've found that does not depend on specific parser/internal data but can rewrite metadata from the parser to AVCodecContext. Adding there something like:

{{{
%    FILL(width);
%    FILL(height);
}}}

correctly propagates video resolution further. Unfortunately, this seems to be only part of missing metadata because  format/pix_fmt is not correctly set/propagated either, and neither are other fields there like AVCodecContext's colorspace, color_trc or color_primaries members.

I wasn't able to find a good place to do this in a clean way. For HEVC I see that such metadata is accessible and partially set in `hevc_parser.c` file in `hevc_parse_slice_header()` function which looks currently like:

{{{
%    s->coded_width  = ps->sps->width;
%    s->coded_height = ps->sps->height;
%    s->width        = ps->sps->width  - ow->left_offset - ow->right_offset;
%    s->height       = ps->sps->height - ow->top_offset  - ow->bottom_offset;
%    s->format       = ps->sps->pix_fmt;
%    avctx->profile  = ps->sps->ptl.general_ptl.profile_idc;
%    avctx->level    = ps->sps->ptl.general_ptl.level_idc;
}}}

while it sets the parser's metadata, it is not propagated forward (only profile and level here seems to be propagated forward).

----

In the end, I think that this can affect negatively performance (fallback to decoding just to get metadata from the stream) and actually makes it impossible to obtain stream information (metadata such as resolution, color space, etc.) through parsers and `avformat_find_stream_info()` function and as such should have high priority for fixing it."	enhancement	new	wish	avcodec	git-master		hevc	ddyndo@vewd.com			0	0