FrameAccess.hpp File Reference

Classifies a stream by what reaching an arbitrary frame costs. More...

Detailed Description

Classifies a stream by what reaching an arbitrary frame costs.

Scrubbing to a frame means decoding from the keyframe before it, so the longest run of non-keyframes bounds the cost of any seek, on every machine.

AV_CODEC_PROP_INTRA_ONLY is not set for CineForm, PNG, FFV1 or all-intra H.264 / HEVC / MPEG-2 (AVC-Intra, XAVC-I, IMX), so the stream itself is read: a container index covering every frame (MP4, MOV) when there is one, else the keyframe flags of the first demuxed packets. Matroska indexes only some keyframes; MPEG-TS and MXF have no index.

Go to the source code of this file.

Classes
struct	Video::FrameAccessProbe

Functions
FrameAccess	Video::keyframe_probe::fromGap (int gap) noexcept
bool	Video::keyframe_probe::canSeek (const AVFormatContext &fmt) noexcept
FrameAccessProbe	Video::keyframe_probe::fromIndex (const AVStream &st) noexcept
	Longest non-keyframe run from an index that lists every frame.
FrameAccessProbe	Video::keyframe_probe::fromPackets (const char *url) noexcept
FrameAccessProbe	Video::classifyFrameAccess (AVFormatContext &fmt, AVStream &st, const char *url) noexcept

Variables
constexpr int	Video::keyframe_probe::max_short_gop = 15
	XDCAM HD and HDV use 12- to 15-frame GOPs: still worth replaying on a seek.

Function Documentation

classifyFrameAccess()

FrameAccessProbe Video::classifyFrameAccess ( AVFormatContext &  fmt, AVStream &  st, const char *  url  )

inlinenoexcept

Parameters

url	what fmt was opened from; the packet probe opens it again so that fmt is not moved.

fromPackets()

FrameAccessProbe Video::keyframe_probe::fromPackets ( const char *  url )

inlinenoexcept

Reads keyframe flags off the first packets of the first video stream, through a context of its own: some demuxers cannot be rewound afterwards (no timestamps to seek on, no byte seeking either).