Public Attributes

vpx_codec_enc_cfg Struct Reference
[Encoder Algorithm Interface]

Encoder configuration structure. More...

#include <vpx_encoder.h>

Collaboration diagram for vpx_codec_enc_cfg:

List of all members.

Public Attributes

unsigned int g_usage
 Algorithm specific "usage" value.
unsigned int g_threads
 Maximum number of threads to use.
unsigned int g_profile
 Bitstream profile to use.
unsigned int g_w
 Width of the frame.
unsigned int g_h
 Height of the frame.
struct vpx_rational g_timebase
 Stream timebase units.
unsigned int g_error_resilient
 Enable error resilient mode.
enum vpx_enc_pass g_pass
 Multi-pass Encoding Mode.
unsigned int g_lag_in_frames
 Allow lagged encoding.
unsigned int rc_dropframe_thresh
 Temporal resampling configuration, if supported by the codec.
unsigned int rc_resize_allowed
 Enable/disable spatial resampling, if supported by the codec.
unsigned int rc_resize_up_thresh
 Spatial resampling up watermark.
unsigned int rc_resize_down_thresh
 Spatial resampling down watermark.
enum vpx_rc_mode rc_end_usage
 Rate control algorithm to use.
struct vpx_fixed_buf rc_twopass_stats_in
 Two-pass stats buffer.
unsigned int rc_target_bitrate
 Target data rate.
unsigned int rc_min_quantizer
 Minimum (Best Quality) Quantizer.
unsigned int rc_max_quantizer
 Maximum (Worst Quality) Quantizer.
unsigned int rc_undershoot_pct
 Rate control undershoot tolerance.
unsigned int rc_overshoot_pct
 Rate control overshoot tolerance.
unsigned int rc_buf_sz
 Decoder Buffer Size.
unsigned int rc_buf_initial_sz
 Decoder Buffer Initial Size.
unsigned int rc_buf_optimal_sz
 Decoder Buffer Optimal Size.
unsigned int rc_2pass_vbr_bias_pct
 Two-pass mode CBR/VBR bias.
unsigned int rc_2pass_vbr_minsection_pct
 Two-pass mode per-GOP minimum bitrate.
unsigned int rc_2pass_vbr_maxsection_pct
 Two-pass mode per-GOP maximum bitrate.
enum vpx_kf_mode kf_mode
 Keyframe placement mode.
unsigned int kf_min_dist
 Keyframe minimum interval.
unsigned int kf_max_dist
 Keyframe maximum interval.

Detailed Description

Encoder configuration structure.

This structure contains the encoder settings that have common representations across all codecs. This doesn't imply that all codecs support all features, however.


Member Data Documentation

Enable error resilient mode.

Error resilient mode indicates to the encoder that it should take measures appropriate for streaming over lossy or noisy links, if possible. Set to 1 to enable this feature, 0 to disable it.

unsigned int vpx_codec_enc_cfg::g_h

Height of the frame.

This value identifies the presentation resolution of the frame, in pixels. Note that the frames passed as input to the encoder must have this resolution. Frames will be presented by the decoder in this resolution, independent of any spatial resampling the encoder may do.

Allow lagged encoding.

If set, this value allows the encoder to consume a number of input frames before producing output frames. This allows the encoder to base decisions for the current frame on future frames. This does increase the latency of the encoding pipeline, so it is not appropriate in all situations (ex: realtime encoding).

Note that this is a maximum value -- the encoder may produce frames sooner than the given limit. Set this value to 0 to disable this feature.

Multi-pass Encoding Mode.

This value should be set to the current phase for multi-pass encoding. For single pass, set to VPX_RC_ONE_PASS.

Bitstream profile to use.

Some codecs support a notion of multiple bitstream profiles. Typically this maps to a set of features that are turned on or off. Often the profile to use is determined by the features of the intended decoder. Consult the documentation for the codec to determine the valid values for this parameter, or set to zero for a sane default. profile of bitstream to use

Maximum number of threads to use.

For multi-threaded implementations, use no more than this number of threads. The codec may use fewer threads than allowed. The value 0 is equivalent to the value 1.

Stream timebase units.

Indicates the smallest interval of time, in seconds, used by the stream. For fixed frame rate material, or variable frame rate material where frames are timed at a multiple of a given clock (ex: video capture), the RECOMMENDED method is to set the timebase to the reciprocal of the frame rate (ex: 1001/30000 for 29.970 Hz NTSC). This allows the pts to correspond to the frame number, which can be handy. For re-encoding video from containers with absolute time timestamps, the RECOMMENDED method is to set the timebase to that of the parent container or multimedia framework (ex: 1/1000 for ms, as in FLV).

Algorithm specific "usage" value.

Algorithms may define multiple values for usage, which may convey the intent of how the application intends to use the stream. If this value is non-zero, consult the documentation for the codec to determine its meaning.

unsigned int vpx_codec_enc_cfg::g_w

Width of the frame.

This value identifies the presentation resolution of the frame, in pixels. Note that the frames passed as input to the encoder must have this resolution. Frames will be presented by the decoder in this resolution, independent of any spatial resampling the encoder may do.

Keyframe maximum interval.

This value, expressed as a number of frames, forces the encoder to code a keyframe if one has not been coded in the last kf_max_dist frames. A value of 0 implies all frames will be keyframes. Set kf_min_dist equal to kf_max_dist for a fixed interval.

Keyframe minimum interval.

This value, expressed as a number of frames, prevents the encoder from placing a keyframe nearer than kf_min_dist to the previous keyframe. At least kf_min_dist frames non-keyframes will be coded before the next keyframe. Set kf_min_dist equal to kf_max_dist for a fixed interval.

Keyframe placement mode.

This value indicates whether the encoder should place keyframes at a fixed interval, or determine the optimal placement automatically (as governed by the kf_min_dist and kf_max_dist parameters)

Two-pass mode CBR/VBR bias.

Bias, expressed on a scale of 0 to 100, for determining target size for the current frame. The value 0 indicates the optimal CBR mode value should be used. The value 100 indicates the optimal VBR mode value should be used. Values in between indicate which way the encoder should "lean." RC mode bias between CBR and VBR(0-100: 0->CBR, 100->VBR)

Two-pass mode per-GOP maximum bitrate.

This value, expressed as a percentage of the target bitrate, indicates the maximum bitrate to be used for a single GOP (aka "section")

Two-pass mode per-GOP minimum bitrate.

This value, expressed as a percentage of the target bitrate, indicates the minimum bitrate to be used for a single GOP (aka "section")

Decoder Buffer Initial Size.

This value indicates the amount of data that will be buffered by the decoding application prior to beginning playback. This value is expressed in units of time (milliseconds). Use the target bitrate (rc_target_bitrate) to convert to bits/bytes, if necessary.

Decoder Buffer Optimal Size.

This value indicates the amount of data that the encoder should try to maintain in the decoder's buffer. This value is expressed in units of time (milliseconds). Use the target bitrate (rc_target_bitrate) to convert to bits/bytes, if necessary.

Decoder Buffer Size.

This value indicates the amount of data that may be buffered by the decoding application. Note that this value is expressed in units of time (milliseconds). For example, a value of 5000 indicates that the client will buffer (at least) 5000ms worth of encoded data. Use the target bitrate (rc_target_bitrate) to convert to bits/bytes, if necessary.

Temporal resampling configuration, if supported by the codec.

Temporal resampling allows the codec to "drop" frames as a strategy to meet its target data rate. This can cause temporal discontinuities in the encoded video, which may appear as stuttering during playback. This trade-off is often acceptable, but for many applications is not. It can be disabled in these cases.

Note that not all codecs support this feature. All vpx VPx codecs do. For other codecs, consult the documentation for that algorithm.

This threshold is described as a percentage of the target data buffer. When the data buffer falls below this percentage of fullness, a dropped frame is indicated. Set the threshold to zero (0) to disable this feature.

Rate control algorithm to use.

Indicates whether the end usage of this stream is to be streamed over a bandwidth constrained link, indicating that Constant Bit Rate (CBR) mode should be used, or whether it will be played back on a high bandwidth link, as from a local disk, where higher variations in bitrate are acceptable.

Maximum (Worst Quality) Quantizer.

The quantizer is the most direct control over the quality of the encoded image. The range of valid values for the quantizer is codec specific. Consult the documentation for the codec to determine the values to use. To determine the range programmatically, call vpx_codec_enc_config_default() with a usage value of 0.

Minimum (Best Quality) Quantizer.

The quantizer is the most direct control over the quality of the encoded image. The range of valid values for the quantizer is codec specific. Consult the documentation for the codec to determine the values to use. To determine the range programmatically, call vpx_codec_enc_config_default() with a usage value of 0.

Rate control overshoot tolerance.

This value, expressed as a percentage of the target bitrate, describes the maximum allowed bitrate for a given frame. Set to zero to use the codec default.

Enable/disable spatial resampling, if supported by the codec.

Spatial resampling allows the codec to compress a lower resolution version of the frame, which is then upscaled by the encoder to the correct presentation resolution. This increases visual quality at low data rates, at the expense of CPU time on the encoder/decoder.

Spatial resampling down watermark.

This threshold is described as a percentage of the target data buffer. When the data buffer falls below this percentage of fullness, the encoder will step down to a lower resolution version of the frame.

Spatial resampling up watermark.

This threshold is described as a percentage of the target data buffer. When the data buffer rises above this percentage of fullness, the encoder will step up to a higher resolution version of the frame.

Target data rate.

Target bandwidth to use for this stream, in kilobits per second.

Two-pass stats buffer.

A buffer containing all of the stats packets produced in the first pass, concatenated.

Rate control undershoot tolerance.

This value, expressed as a percentage of the target bitrate, describes the target bitrate for easier frames, allowing bits to be saved for harder frames. Set to zero to use the codec default.


The documentation for this struct was generated from the following file: