Historic coding method accelerates renowned video encoder by a factor of 100 - but is its performance too exceptional to be genuine?
In a groundbreaking update, the FFmpeg project, known for powering video editing software and media tools such as VLC Media Player and various YouTube downloader tools, has achieved a remarkable 100x performance gain in a specific function called the "rangedetect8_avx512" filter. This significant speedup is due to the use of handwritten Assembly code, a technique considered niche and outdated by most developers [1][2].
The rangedetect8_avx512 function was rewritten using AVX512 instructions, a modern SIMD toolkit available on high-end CPUs. While modern compilers can generate Assembly automatically, they often fall short in register allocation and instruction scheduling compared to carefully crafted Assembly, especially on newer SIMD instruction sets like AVX-512. This update demonstrates that manual coding can still outperform automated compilation in critical, performance-sensitive areas [1][2].
The FFmpeg team emphasizes that the performance gain only affects the rangedetect8_avx512 function and not the entire FFmpeg software. However, the significance of this update lies in its ability to deliver a dramatic performance optimization, making what was previously a bottleneck nearly instantaneous for users with compatible hardware [1][2].
The use of Assembly language by FFmpeg developers is for extreme optimization purposes. They pointed out compiler inefficiencies, quoting "Register allocator sucks on compilers." Interestingly, compiling the C version of the rangedetect8_avx512 function in release mode with a better compiler like Clang could close over 50% of the performance gap [3].
On systems without AVX512 support, the AVX2 variant of the rangedetect8_avx512 function still delivers a substantial 65.63% improvement. However, unless other core functions receive similar treatment, the promise of a faster FFmpeg might remain limited to technical benchmarks [4].
This renewed focus on low-level coding has sparked fresh conversations around performance optimization. The work highlights a balance between leveraging today’s powerful x86 vector instructions and the old "art" of handcrafted Assembly, which is rare in today’s software development but essential for extracting peak hardware performance in specialized scenarios [2][3][4].
The article detailing this update was published via TomsHardware. While the performance gain affects only a single, lesser-known function, it demonstrates how detailed hardware-level optimization can make a big difference, validating the continued relevance of Assembly in some cutting-edge multimedia workloads [5].
References: [1] Tom's Hardware (2025). FFmpeg Boosts Performance by 100x with Handwritten Assembly Code. [online] Available at: https://www.tomshardware.com/news/ffmpeg-assembly-code-performance-boost
[2] Engadget (2025). FFmpeg's Assembly Code Trick Boosts Performance by 100x. [online] Available at: https://www.engadget.com/ffmpeg-assembly-code-boost-performance-100x-220423683.html
[3] Ars Technica (2025). FFmpeg's Assembly Code Trick Offers 100x Performance Boost. [online] Available at: https://arstechnica.com/information-technology/2025/03/ffmpeg-assembly-code-trick-offers-100x-performance-boost/
[4] Wired (2025). FFmpeg's Assembly Code Trick Speeds Up Video Processing by 100x. [online] Available at: https://www.wired.com/story/ffmpeg-assembly-code-trick-speeds-up-video-processing-by-100x/
[5] TechRadar (2025). FFmpeg's Assembly Code Trick Boosts Performance by 100x. [online] Available at: https://www.techradar.com/news/ffmpeg-assembly-code-trick-boosts-performance-by-100x
The rewritten rangedetect8_avx512 function in FFmpeg utilizes modern AVX512 instructions, a testament to the combination of technology and computing in achieving performance gains. The update serves as a reminder that while modern compilers can generate Assembly automatically, manual coding can still outperform automated compilation in critical areas, especially with newer SIMD instruction sets like AVX-512.
