cs.CVOct 8, 2026
SaveSP-DocReader: Difference-Aware Self-Play for Precise Document OCR
Organizations: Guangdong OPPO Mobile Telecommunications Corp.,Ltd · Adelaide University
Abstract
Accurate page transcription remains difficult for vision language models under limited input and training budgets. We present SP-DocReader, a self-play framework for optical character recognition (OCR) that targets residual errors after supervised fine-tuning. Reading Discrepancy Masking aligns reference and generated model tokens through a longest common subsequence, then scores unmatched positions with their full conditioning prefixes. Focused Fidelity Loss adds direct negative log-likelihood supervision at unmatched ground-truth positions. Only the OCR module is trained, while the backbone remains frozen. We derive the combined gradient to distinguish relative score optimization from direct supervision. Compared with SFT-2, SP-DR-3 reduces Vary-600K character error rate on both backbones. On Qwen3-VL-4B, it reduces character error rate by approximately 54 percent and improves DocVQA Average Normalized Levenshtein Similarity (ANLS) by 3.7 points. These results show the value of focusing self-play training on the discrepancies that remain after supervised fine-tuning.
Figures & tables
Figure 1: Overview of the SP-DocReader training framework. A frozen opponent generates a synthetic reading of the document, and Reading Discrepancy Masking aligns it with the ground truth to isolate the errors. The main player then optimizes a dual objective that combines the Reading Discrepancy Loss for difference-aware correction with the Focused Fidelity Loss for direct supervision on the hard tokens, after which the opponent is refreshed.
Figure 2: Fixed and refreshed self-play training on Qwen3-VL-4B. Green circles show the fixed-reading branch from its starting checkpoint through five local epochs. The red diamond represents a single checkpoint after two local epochs in the refreshed second round, which updates the opponent, generated readings, and discrepancy masks. The panels report Vary-600K NED, DocBank NED, DocVQA ANLS, and their mean, with NED scaled to 0–100 for the mean. The refreshed checkpoint scores higher than the fifth fixed-reading epoch in every panel.
Figure 3: Reported Qwen3-VL-4B comparisons across training-page budgets, source-image resolutions and relative training costs. Panel (a) averages Vary-600K, DocBank and IIT-CDIP NED with DocVQA and InfographicVQA ANLS, weighting each dataset equally and scaling NED by 100. Panel (b) compares CER at four resolutions. Panel (c) uses the mean of DocBank, IIT-CDIP NED, DocVQA and InfographicVQA ANLS.
Figure 4: Qualitative comparisons on two low-resolution documents. Blue, green and red dashed boxes contain the reference, supervised and SP-DocReader readings, respectively. SP-DocReader corrects the discrepancies.
Appendix figures & tables5 assets
Supplementary material from the paper’s appendix.
Appendix
| Models | Method | CER(%) | WER(%) | NED | Token-F1 | ROUGE-L | BLEU-4 | AVG |
|---|---|---|---|---|---|---|---|---|
| InternVL 3.5-4B | Base | 4.85 | 9.12 | 0.938 | 0.941 | 87.29 | 80.44 | 88.91 |
| SFT-1 | 2.31 ( -2.54 ) | 4.60 ( -4.52 ) | 0.969 ( +0.031 ) | 0.972 ( +0.031 ) | 92.87 ( +5.58 ) | 88.32 ( +7.88 ) | 93.82 ( +4.91 ) | |
| SFT-2 | 2.12 ( -0.19 ) | 4.00 ( -0.60 ) | 0.971 ( +0.002 ) | 0.975 ( +0.003 ) | 93.39 ( +0.52 ) | 89.04 ( +0.72 ) | 94.26 ( +0.44 ) | |
| SFT-3 | 2.34 ( +0.22 ) | 4.37 ( +0.37 ) | 0.968 ( -0.003 ) | 0.976 ( +0.001 ) | 92.93 ( -0.46 ) | 88.60 ( -0.44 ) | 93.98 ( -0.28 ) | |
| SP-DR-1 | 1.77 ( -0.35 ) | 3.49 ( -0.51 ) | 0.978 ( +0.007 ) | 0.982 ( +0.007 ) | 95.28 ( +1.89 ) | 91.43 ( +2.39 ) | 95.68 ( +1.42 ) | |
| SP-DR-2 | 1.35 ( -0.42 ) | 2.83 ( -0.66 ) | 0.984 ( +0.006 ) | 0.989 ( +0.007 ) | 96.77 ( +1.49 ) | 93.01 ( +1.58 ) | 96.77 ( +1.09 ) |
Table 5: Full reading accuracy on the Vary-600K validation set across all supervised epochs and self-play rounds. Each cell shows the change over the previous row, and SP-DR-1 is measured against SFT-2. Improvements are in red and regressions in blue. AVG is the mean of NED, Token-F1, ROUGE-L, and BLEU-4 on a 0 to 100 scale. SP-DR-3 is the model reported in the main text.
| Models | Method | DocBank | IIT-CDIP | VQA (ANLS ) | AVG | |||
|---|---|---|---|---|---|---|---|---|
| CER(%) | NED | CER(%) | NED | DocVQA | InfoVQA | |||
| InternVL 3.5-4B | Base | 13.44 | 0.812 | 19.56 | 0.735 | 72.79 | 50.52 | 69.50 |
| SFT-1 | 12.40 ( -1.04 ) | 0.835 ( +0.023 ) | 18.39 ( -1.17 ) | 0.762 ( +0.027 ) | 72.71 ( -0.08 ) | 49.20 ( -1.32 ) | 70.40 ( +0.90 ) | |
| SFT-2 | 11.60 ( -0.80 ) | 0.848 ( +0.013 ) | 17.83 ( -0.56 ) | 0.778 ( +0.016 ) | 73.01 ( +0.30 ) | 48.15 ( -1.05 ) | 70.94 ( +0.54 ) | |
| SFT-3 | 12.17 ( +0.57 ) | 0.829 ( -0.019 ) | 18.44 ( +0.61 ) | 0.762 ( -0.016 ) | 72.52 ( -0.49 ) | 48.24 ( +0.09 ) | 69.97 ( -0.97 ) | |
| SP-DR-1 | 10.55 ( -1.05 ) | 0.866 ( +0.018 ) | 16.70 ( -1.13 ) | 0.802 ( +0.024 ) | 73.48 ( +0.47 ) | 48.40 ( +0.25 ) | 72.17 ( +1.23 ) | |
Table 6: Full zero-shot trajectories on DocBank, IIT-CDIP, DocVQA, and InfographicVQA. Each cell shows the change over the previous row, and SP-DR-1 is measured against SFT-2. Improvements are in red and regressions in blue. AVG is the mean of the two NED scores and the two ANLS scores on a 0 to 100 scale. SP-DR-3 is the model reported in the main text.
| Config | Method | Vary CER(%) | DocBank NED | IIT-CDIP NED | DocVQA | InfoVQA | AVG |
|---|---|---|---|---|---|---|---|
| Full tuning | SFT-2 | 2.25 | 0.872 | 0.805 | 81.00 | 55.00 | 75.92 |
| Iter-1 | 1.55 ( -0.70 ) | 0.878 ( +0.006 ) | 0.812 ( +0.007 ) | 81.50 ( +0.50 ) | 55.30 ( +0.30 ) | 76.45 ( +0.53 ) | |
| Iter-2 | 1.18 ( -0.37 ) | 0.871 ( -0.007 ) | 0.804 ( -0.008 ) | 81.10 ( -0.40 ) | 54.60 ( -0.70 ) | 75.80 ( -0.65 ) | |
| Iter-3 | 0.98 ( -0.20 ) | 0.862 ( -0.009 ) | 0.795 ( -0.009 ) | 80.41 ( -0.69 ) | 53.80 ( -0.80 ) | 74.98 ( -0.82 ) | |
| Iter-4 | 0.95 ( -0.03 ) | 0.851 ( -0.011 ) | 0.786 ( -0.009 ) | 79.80 ( -0.61 ) | 53.10 ( -0.70 ) | 74.15 ( -0.83 ) | |
| Iter-5 | 0.94 ( -0.01 ) | 0.843 ( -0.008 ) | 0.779 ( -0.007 ) | 79.50 ( -0.30 ) | 52.70 ( -0.40 ) | 73.60 ( -0.55 ) |
Table 7: Modality-specific analysis on Qwen3-VL-4B. Full tuning updates the backbone and the OCR module, while the modular design freezes the backbone. The Vary-600K column measures in-distribution reading, and AVG averages the four zero-shot scores on a 0 to 100 scale. Each cell shows the change over the previous row, with improvements in red and regressions in blue.
| Vary 600K Example 1 | Ground Truth:"<lb><lb>Our recursive calls to Quicksort use this index (splitPoint) to reduce the size of the problem in the general case.<lb>Quicksort(first, splitPoint – 1) sorts the left “half” of the array. Quick-sort(splitPoint + 1, last) sorts the right “half” of the array. (The “halves” are not necessarily the same size.) splitVal is already in its correct position in data[splitPoint].<lb>What is the base case? When the segment being examined has only one item, we do not need to go on. That is represented in the algorithm by the missing else statement. If there is only one value in the segment being sorted, it is already in its place.<lb>We must find a way to get all elements that are equal to or less than splitVal on one side of splitVal and all elements that are greater than splitVal on the other side. We do this by moving a pair of the indexes from the ends toward the middle of the array, looking for items that are on the wrong side of the split value. When we find pairs that are on the wrong side, we swap them and continue working our way into the middle of the array.<lb> \begin{tabular}{|c|} <lb> \hline \ <lb> \end{tabular} <lb>" |
| SFT-2 | Document Reading:"<lb><lb>Our recurslve calls to Quicksort use this index (splitPoint) to reduce the size of the problem in the genral case.<lb> Quicksort(first, splitPoint - 1) sorts the left “half” of the array. Quicksort (splitPoint + 1, last) sorts the right “half” of the arry . (The “halves” are not necessarily the same size.) splitval is already in its correct position in data[splitPoint].<lb> What is the base case? When the segment being examned has only one item, we do not need to go on. That is represented in the algorithm by the missing else statement. If there is only one value in the segment being sorted, it is already in its place.<lb> We must find a way to get all elements that are equal to or less than splitVal on one side of splitVal and all elements that are greater than splitVal on the other side. we do this by moving a pair of the indices from the ends toward the middle of the array, looking for items that are on the wrong side of the split value. When we find pairs that are on the wrong side, we swap them and continue working our way into the middle of the array.<lb> \begin{tabular}{ |c } <lb> \hline \ <lb> \end{tabular} <lb> " |
| SP-DocReader iteration 3 | Document Reading:"<lb><lb>Our recursive calls to Quicksort use this index (splitPoint) to reduce the size of the problem in the general case.<lb> Quicksort(first, splitPoint - 1) sorts the left “half” of the array. Quicksort (splitPoint + 1, last) sorts the right “half” of the array. (The “halves” are not necessarly the same size.) splitVal is already in its correct position in data[splitPoint].<lb> What is the base case? When the segment being examined has only one item, we do not need to go on. That is represented in the algorithm by the missing else statement. If there is only one value in the segment being sorted, it is already in its place.<lb> We must find a way to get all elements that are equal to or less than splitVal on one side of splitVal and all elements that are greater than splitVal on the other side. We do this by moving a pair of the indixes from the ends toward the middle of the array, looking for items that are on the wrong side of the split value. When we find pairs that are on the wrong side, we swap them and continue working our way into the middle of the array.<lb> \begin{tabular}{|c|} <lb> \hline \ <lb> \end{tabular} <lb> " |
Table 8: Vary-600K Example 1, a Quicksort page, with the supplied reference text and reported readings. The reference does not cover the full page shown in the thumbnail. Red shading marks differences from the displayed reference without changing the readings.
| Vary 600K Example 2 | Ground Truth:"<lb>Summa Theologica Saint Thomas Aquinas<lb>will reflect honor on the whole state: as when he brings to effect what the whole state is striving for.<lb>Reply to Objection 4: The chief act of virtue is the inward choice, and a virtue may have this without outward fortune: so that even a poor man may be magnificent. But goods of fortune are requisite as instruments to the external acts of virtue: and in this way a poor man cannot accomplish the outward act of magnificence in things that are great simply. Perhaps, however, he may be able to do so in things that are great by comparison to some particular work; which, though little in itself, can nevertheless be done magnificently in proportion to its genus: for little and great are relative terms, as the Philosopher says (De Praedic. Cap. Ad aliquid.).<lb>Whether magnificence is a part of fortitude?<lb>Objection 1: It seems that magnificence is not a part of fortitude. For magnificence agrees in matter with liberality, as stated above (A[3]). But liberality is a part, not of fortitude, but of justice. Therefore magnificence is not a part of fortitude.<lb>Objection 2: Further, fortitude is about fear and darings. But magnificence seems to have nothing to do with fear, but only with expenditure, which is a kind of action. Therefore magnificence seems to pertain to justice, which is about actions, rather than to fortitude.<lb>Objection 3: Further, the Philosopher says (Ethic. iv, 2) that "the magnificent man is like the man of science." Now science has more in common with prudence than with fortitude. Therefore magnificence should not be reckoned a part of fortitude.<lb>On the contrary, Tully (De Invent. Rhet. ii) and Macrobius (De Somn. Scip. i) and Andronicus reckon magnificence to be a part of fortitude.<lb>I answer that, Magnificence, in so far as it is a special virtue, cannot be reckoned a subjective part of fortitude, since it does not agree with this virtue in the point of matter: but it is reckoned a part thereof, as being annexed to it as secondary to principal virtue.<lb>In order for a virtue to be annexed to a principal virtue, two things are necessary, as stated above (Q[80]). The one is that the secondary virtue agree with the principal, and the other is that in some respect it be exceeded thereby. Now magnificence agrees with fortitude in the point that as fortitude tends to something arduous and difficult, so also does magnificence: wherefore seemingly it is seated, like fortitude, in the irascible. Yet magnificence falls short of fortitude, in that the arduous thing to which fortitude tends derives its difficulty from a danger that threatens the person, whereas the arduous thing to which magnificence tends, derives its difficulty from the dispossession of one’s property, which is of much less account than danger to one’s person. Wherefore magnificence is accounted a part of fortitude.<lb>Reply to Objection 1: Justice regards operations in themselves, as viewed under the aspect of something due: but liberality and magnificence regard sumptuary operations as related to the passions of the soul, albeit in different ways. For liberality regards expenditure in reference to the love and desire of money, which are passions of the concupiscible faculty, and do not hinder the<lb>2581<lb>" |
| SFT-2 | Document Reading:"<lb>Summa Theologica Saint Thomas Aquinas<lb> will reflect honor on the whole state: as when he brings to affect what the whole state is striving for.<lb> Reply to Objection 4: The chief act of virtue is the inward choice, and a virtue may have this without outward fortune: so that even a poor man may be magnificent. But goods of fortune are requisite as instruments to the external acts of virtue: and in this way a poor man cannot accomplish the outward act of magnificence in things that are great simply. Perhaps, however, he may be able to do so in things that are great by comparison to some particular work; which, though little in itself, can nevertheless be done magnificently in proportion to its genus: for little and great are relative terms, as the Philosopher says (De Predic . Cap. Ad aliqid .).<lb> Whether magnificence is a part of fortitude?<lb> Objection 1: It seems that magnificence is not a part of fortitude. For magnificence agrees in matter with liberality, as stated above (A[3]). But liberality is a part, not of fortitude, but of justice. Therefore magnificence is not a part of fortitude.<lb> Objection 2: Further, fortitude is about fear and daring . But magnificence seems to have nothing to do with fear, but only with expenditure, which is a kind of action. Therefore magnificence seems to pertain to justice, which is about actions, rather than to fortitude.<lb> Objection 3: Further, the Philosopher says (Ethic. iv, 2) that "the magnificent man is like the man of science." Now science has more in common with prudence than with fortitude. Therefore magnificence should not be reckoned a part of fortitude.<lb> On the contrary, Tully (De Invent. Rhet. ii) and Marcrobius (De Somn. Scp . i) and Andronicus reckon magnificence to be a part of fortitude.<lb> I answer that, Magnificence, in so far as it is a special virtue, cannot be reckond a subjective part of fortitude, since it does not agree with this virtue in the point of matter: but it is reckoned a part thereof, as being anexed to it as secondary to principal virtue.<lb> In order for a virtue to be annexed to a principal virtue, two things are necessary, as stated above (Q[80]). The one is that the secondary virtue agree with the principal, and the other is that in some respect it be exceeded thereby. Now magnificence agrees with fortitude in the point that as fortitude tends to something arduous and difficult, so also does magnificence: wherefore seemingly it is seated, like fortitude, in the irrascible . Yet magnificence falls short of fortitude, in that the arduous thing to which fortitude tends derives its difficulty from a danger that threatens the person, whereas the arduous thing to which magnificence tends, derives its difficulty from the dispossesion of one’s property, which is of much less acount than danger to one’s person. Wherefore magnificence is accounted a part of fortitude.<lb> Reply to Objection 1: Justice regards operations in themselves, as viewed under the aspect of something due: but liberality and magnificence regard sumptary operations as related to the passions of the soul, albit in different ways. For liberality regards expenditure in reference to the love and desire of money, which are passions of the concupiscble faculty, and do not hinder the<lb> 258I <lb>" |
| SP-DocReader iteration 3 | Document Reading:"<lb>Summa Theologica Saint Thomas Aquinas<lb> will reflect honor on the whole state: as when he brings to effect what the whole state is striving for.<lb> Reply to Objection 4: The chief act of virtue is the inward choice, and a virtue may have this without outward fortune: so that even a poor man may be magnificent. But goods of fortune are requisite as instruments to the external acts of virtue: and in this way a poor man cannot accomplish the outward act of magnificence in things that are great simply. Perhaps, however, he may be able to do so in things that are great by comparison to some particular work; which, though little in itself, can nevertheless be done magnificently in proportion to its genus: for little and great are relative terms, as the Philosopher says (De Praedlc . Cap. Ad aliquld .).<lb> Whether magnificence is a part of fortitude?<lb> Objection 1: It seems that magnificence is not a part of fortitude. For magnificence agrees in matter with liberality, as stated above (A[3]). But liberality is a part, not of fortitude, but of justice. Therefore magnificence is not a part of fortitude.<lb> Objection 2: Further, fortitude is about fear and daring . But magnificence seems to have nothing to do with fear, but only with expenditure, which is a kind of action. Therefore magnificence seems to pertain to justice, which is about actions, rather than to fortitude.<lb> Objection 3: Further, the Philosopher says (Ethic. iv, 2) that "the magnificent man is like the man of science." Now science has more in common with prudence than with fortitude. Therefore magnificence should not be reckoned a part of fortitude.<lb> On the contrary, Tully (De Invent. Rhet. ii) and Macrobius (De Somn. Scip. 1 ) and Andronicus reckon magnificence to be a part of fortitude.<lb> I answer that, Magnificence, in so far as it is a special virtue, cannot be reckoned a subjective part of fortitude, since it does not agree with this virtue in the point of matter: but it is reckoned a part thereof, as being annexed to it as secondary to principal virtue.<lb> In order for a virtue to be annexed to a principal virtue, two things are necessary, as stated above (Q[80]). The one is that the secondary virtue agree with the principal, and the other is that in some respect it be exceeded thereby. Now magnificence agrees with fortitude in the point that as fortitude tends to something arduous and difficult, so also does magnificence: wherefore seemingly it is seated, like fortitude, in the irascible. Yet magnificence falls short of fortitude, in that the ardous thing to which fortitude tends derives its difficulty from a danger that threatens the person, whereas the arduous thing to which magnificence tends, derives its difficulty from the disposession of one’s property, which is of much less account than danger to one’s person. Wherefore magnificence is accounted a part of fortitude.<lb> Reply to Objection 1: Justice regards operations in themselves, as viewed under the aspect of something due: but liberality and magnificence regard sumptury operations as related to the passions of the soul, albet in different ways. For liberality regards expenditure in reference to the love and desire of money, which are passions of the concupiscibe faculty, and do not hinder the<lb> 2581<lb>" |
Table 9: Vary-600K Example 2, a Summa Theologica page, with the supplied reference text and reported readings. The thumbnail identifies the source page. Red shading marks differences from the displayed reference without changing the readings.