#6596: G726 codec suspected to not comply with ITU standard -------------------------------------+------------------------------------- Reporter: | Type: defect alban.meffre | Priority: critical Status: new | Version: git- Component: avformat | master Keywords: G726 ITU | Blocked By: standard compliance | Reproduced by developer: 0 Blocking: | Analyzed by developer: 0 | -------------------------------------+------------------------------------- the G726 codec ffmpeg implementation seems not to comply with ITU standard below are the files and commands needed to perform verification *** test vectors *** original test vectors from the ITU in ASCII format (https://www.itu.int/net/itu-t/sigdb/speaudio/Gseries.htm) NRM.M : the test input vector encoded in mu law (sample rate 8kHz, mono) RN24FM.I : the expected result , unpacked to right justified codes input_mulaw.bin : binary version of the above NRM.M input file input_mulaw.wav : playable version $ ffmpeg -f mulaw -ar 8000 -i input_mulaw.bin -acodec copy input_mulaw.wav *** encoding with ITU compliant G726 encoder *** g726encode.exe : g726 encoder from the ITU-T user's group on software tools output_g726.bin : output result $ g726encode.exe -3 -u -i input_mulaw.bin -o output_g726.bin *** binary comparison between output and ITU test vector *** RN24FM.bin : bit packed binary version of the above RN24FM.I file !!!!!! these two file's contents are identical -> g726encode.exe IS ITU compliant !!!!!! *** decode and listen to the result *** output_g726_decoded_pcm_s16le.bin : decoded result of g726encode.exe $ g726decode.exe -3 -l -i output_g726.bin -o output_g726_decoded_pcm_s16le.bin this file can be played correctely -> g726decode.exe IS ITU compliant too $ ffplay -f s16le -ar 8000 output_g726_decoded_pcm_s16le.bin *** encoding with ffmpeg and listen to the result *** output_g726_ffmpeg.bin : ffmpeg g726 encode output result output_g726_ffmpeg.wav : ffmpeg g726 encode output result (playable) $ ffmpeg -f mulaw -ar 8000 -i input_mulaw.bin -acodec g726 -code_size 3 output_g726_ffmpeg.wav $ ffmpeg -f mulaw -ar 8000 -i input_mulaw.bin -acodec g726 -code_size 3 -f u8 output_g726_ffmpeg.bin output_g726_ffmpeg_decoded_pcm_s16le.bin : decoded result of output_g726_ffmpeg.bin $ g726decode.exe -3 -l -i output_g726_ffmpeg.bin -o output_g726_ffmpeg_decoded_pcm_s16le.bin !!!!!! this file cannot be played correctely -> ffmpeg's implementation of the g726 codec is not compliant with ITU !!!!!! $ ffplay -f s16le -ar 8000 output_g726_ffmpeg_decoded_pcm_s16le.bin -- Ticket URL: <https://trac.ffmpeg.org/ticket/6596> FFmpeg <https://ffmpeg.org> FFmpeg issue tracker