Spatio-Temporal Entropy Model

A Pytorch Reproduction of Spatio-Temporal Entropy Model (STEM) for end-to-end leaned video compression.

More details can be found in the following paper:

Spatiotemporal Entropy Model is All You Need for Learned Video Compression
Alibaba Group, arxiv 2021.4.13
Zhenhong Sun, Zhiyu Tan, Xiuyu Sun, Fangyi Zhang, Dongyang Li, Yichen Qian, Hao Li

Note that It Is Not An Official Implementation Code.

The differences with the original paper are not limited to the following:

The number of model channels are fewer.
The Encoder/Decoder in original paper consists of conditional conv¹ to support various rate in one single model. And the architecture is the same as [2]². However, I only use the single rate Encoder/Decoder with the same architecture as [2]²

ToDo:

1. various rate model training and evaluation.

Environment

Python == 3.7.10
Pytorch == 1.7.1
CompressAI

Dataset

I use the Vimeo90k Septuplet Dataset to train the models. The Dataset contains about 64612 training sequences and 7824 testing sequences. All sequence contains 7 frames.

The train dataset folder structure is as

.dataset/vimeo_septuplet/
│  sep_testlist.txt
│  sep_trainlist.txt
│  vimeo_septuplet.txt
│  
├─sequences
│  ├─00001
│  │  ├─0001
│  │  │      f001.png
│  │  │      f002.png
│  │  │      f003.png
│  │  │      f004.png
│  │  │      f005.png
│  │  │      f006.png
│  │  │      f007.png
│  │  ├─0002
│  │  │      f001.png
│  │  │      f002.png
│  │  │      f003.png
│  │  │      f004.png
│  │  │      f005.png
│  │  │      f006.png
│  │  │      f007.png
...

I evaluate the model on UVG & HEVC TEST SEQUENCE Dataset. The test dataset folder structure is as

.dataset/UVG/
├─PNG
│  ├─Beauty
│  │      f001.png
│  │      f002.png
│  │      f003.png
│  │      ...
│  │      f598.png
│  │      f599.png
│  │      f600.png
│  │      
│  ├─HoneyBee
│  │      f001.png
│  │      f002.png
│  │      f003.png
│  │      ...
│  │      f598.png
│  │      f599.png
│  │      f600.png
│  │     
│  │      ...

.dataset/HEVC/
├─BasketballDrill
│      f001.png
│      f002.png
│      f003.png
│      ...
│      f098.png
│      f099.png
│      f100.png
│      
├─BasketballDrive
│      f001.png
│      f002.png
│      ...

Train Your Own Model

python3 trainSTEM.py -d /path/to/your/image/dataset/vimeo_septuplet –lambda 0.01 -lr 1e-4 –batch-size 16 –model-save /path/to/your/model/save/dir –cuda –checkpoint /path/to/your/iframecompressor/checkpoint.pth.tar

I tried to train with Mean-Scale Hyperprior / Joint Autoregressive Hierarchical Priors / Cheng2020Attn in CompressAI library and find that a powerful I Frame Compressor does have great performance benefits.

Evaluate Your Own Model

python3 evalSTEM.py –checkpoint /path/to/your/iframecompressor/checkpoint.pth.tar –entropy-model-path /path/to/your/stem/checkpoint.pth.tar

Currently only support evaluation on UVG & HEVC TEST SEQUENCE Dataset.

Result

测试数据集UVG	PSNR	BPP	PSNR in paper	BPP in paper
SpatioTemporalPriorModel_Res	36.104	0.087	35.95	0.080
SpatioTemporalPriorModel	36.053	0.080	35.95	0.082
SpatioTemporalPriorModelWithoutTPM	None	None	35.95	0.100
SpatioTemporalPriorModelWithoutSPM	36.066	0.080	35.95	0.087
SpatioTemporalPriorModelWithoutSPMTPM	36.021	0.141	35.95	0.123

PSNR in paper & BPP in paper is estimated from Figure 6 in the original paper.

It seems that the context model SPM has no good effect in my experiments.

I look forward to receiving more feedback on the test results, and feel free to share your test results!

More Informations About Various Rate Model Training

As stated in the original paper, they use a variable-rate auto-encoder to support various rate in one single model. I tried to train STEM with GainedVAE, which is also a various rate model. Some point can achieve comparable r-d performance while others may degrade. What’s more, the interpolation result could have more performance degradation cases.

Probably we need Loss Modulator³ for various rate model training. Read Oren Ripple’s ICCV 2021 paper³ for more details.

Acknowledgement

The framework is based on CompressAI, I add the model in compressai.models.spatiotemporalpriors. And trainSTEM.py/evalSTEM.py is modified with reference to compressai_examples